3 years ago I lost my Father in Law to cancer and since have been trying to help my mother in laws grieving process. We have tried many methods in helping, but have always been met with the same disrespectful attitudes and constant victim playing role. When confronting her about these situations, she blames her children for ganging up and attacking her. As the son in law, i was easily able to remove her from my life and just no talk to her anymore. But as for my wife, i sat back and watched her mental wear herself out on a constant basis trying to save what relationship she could with her. This included nights of crying and angry venting to me. I hate to see my wife go through the constant issues with her mother, and am reaching out to see if there are any techniques or personal experiences that could help this situation?
Background for the past 3 years:
We started off after the passing coming over every weekend and trying to help cope with the issues, but were met with wanting to be alone and grieve. So we did, came over once a month and made her dinner. After the first year, the fighting between mother or daughter began to become a regular basis and when i started to tell my wife that is was unhealthy to continue in that way. We got married that year and went on a week honeymoon out of country, when we returned we call MIL and wanted to tell her about our trip, we were met with "I ate all of your anniversary cake while y'all were gone and I’m not that mad about it, **** happens" upset mother and daughter had some choice words and ended with MIL saying "Y'all don't have to talk to me anymore, i don't care" - this was the first time i stepped in and told them that if they couldn't respect each other and talk civil, then they shouldn't talk at all. Then, I became attacker in her mind and how could I take to someone grieving that way?? A few months went by and began the nights or crying and angry venting towards me from my wife. We were able to become civil around each other and meet for dinners, but nothing was ever really solved.
Year two – Mostly the same, I took a back seat and stay out of the line of fire. This year, MIL had a daughter returning home from out of state (military husband and 2 kids). Plan was for them to move back into mom’s house and save money until out of state house sold / helps MIL around house to get back into shape. My wife and I went to MIL house to help get house ready for the family and kids arrival and were astonished with them condition of the house. Dog and cat urine and the amount of trash were unbearable to even walk in. When talking to her about this with her, we became the attackers and we were making up stuff so that she would not be able to see her grandchildren? Group text between all members, quickly became where we were all attacking her and giving her the excuse to be rude and disrespectful towards her daughters. This is the second time I chimed in and informed her, that if she was going to be disrespectful to her daughters than we would not talk to her anymore. A couple months later sister in law and family moves in with us stays for a month or so. They talk to MIL, but only see each other once they whole time. *MIL lives 5 mins away* I cut off all communications to her (face book, cell, dinners) my wife is starting to see the patterns and is starting too distant herself and shorten phone calls.
Year three: (this year) we get pregnant and have a baby on the way. My wife starts trying to repair the relationship with her mother so that she can be there when baby is born and so forth. MIL starts adventuring out of the house with friends and starting to date other men. Trying to keep it hush hush and get angry when wife talks about it. She gets arrested one night for PI at 3AM and my wife and I have to pick up the car so that it doesn’t get impounded. We start laying out plans for baby arrival, and as her and I am not talking, we inform MIL that when baby come she can be at the hospital, but cannot be in the delivery room with us. This is of course an attack on her and starts up a couple of weeks of fighting between my wife and her. So we inform her she needs to get counseling before she will be allowed around my child, or even come to the hospital.
1 Month before baby arrival: (last night) MIL shows up to house unannounced and wants to talk, we have civil conversation while waiting on wife to get home from work (15-20 mins) then we go to dinner at a restaurant down the road. She informs us she has gone to counseling 3 times and she is trying to change for the better. She mentions that she doesn’t really see the point of it, but is sticking with it. My wife starts the conversation by saying that she and I are very opinionated, and that talking about the issues we have with solve our problems. I tell her that it has always been the same issue for me, that the level of respect that she and her daughters needs to be better. It is understandable to have an argument every once in a while, but every other day, once a week, once a month is really too much. Instantly the she begins to cry and say that I am trying to keep her daughter away from her. My wife tells her that they do not have the relationship they once had because of the way that she treats them, and that she is excited for the days that she can say that they actually had a civil conversation on the phone without fighting, and that is just sad. Then MIL falls back on the grieving and that she is just so sad all the time that must be the reason she is disrespectful to her all the time. I inform her that that is not an excuse and that grieving does not insist of going out partying all night and running around on dates. Feed up we end the dinner and head back home she leaves….

So I understand she did make the effort to come by the house and try to make amends. In my mind, I think she was just trying to come over and sweep everything under the rug so she can be there upon baby arrival. I don’t see that happening now. I know my wife won’t give up on her mother, and I’m not asking her too. I just think she may be enabling her mother actions by trying to calm her after any disagreements with her. Not sure if trying to salvage a relationship is worth it or if I should try to convince my wife to let MIL be until she can move on from this pattern she is in. or maybe we are just “bad kids” and are not seeing the grieving process as it is?

Sorry for the length, but figured more information was needed.
Any similar situations with positive outcomes?