This happened to me a lot when I was younger, only a few times as an adult. As an adult before I got sober, I was so desperate to be "liked" or the laid-back friend who went with the flow I would let it go. Once I got sober and learned how to set boundaries I do not tolerate it more than one time. I value myself and the people I choose to be friends with but it wasn't easy. The last time I was a victim of the "fair-weather friend" I had just gotten sober. Prior to that this friend had been used to me dropping everything to be with them and neglecting other's in order to please them. But anyway. I got sober and this friend who didnt really like the sober sarah had major drama in her family. Drama that i would insert myself in like it was my problem. I had always been letting myself be taken advantage of by her. Her father died suddenly and it was a huge shitshow with her family fighting and her mother acting like a spoiled brat- just terrible. She always cried poor to me and of course she came back for the arrangements and funeral and had no money for funeral clothes. She was also in a bad relationship and her husband was abusive. i took her shopping and got stuff for her and her daughter. I was at the viewing and funeral. I put up with the abuse. (an aside is..she lived in Fl and was cheating on her husband with her other friends' husband and I knew and still didnt say anything and kept her secret). She was fighting with her mom, sister and husband and came to stay at my house and brought along the florida best friend. They were so rude, messy and just helping themselves to everything that I dawned on me- this is not friendship and I am letting myself be taken advantage of. She left and I thought for like two weeks about how to deal with it. I decided on an email. I told her everything that bothered me and gave examples. I basically broke up with her. She wrote something nasty back to me but I never answered. I let that be the last communication I had with her. it was hard but so freeing! It was like a light turned on. That was the last time I ever had boundary issues.