Hi Sweet crusader,
I think that as adults we are all so different from one another - this is why i believe there is no set way for us to be. Also, this is a huge and very interesting subject so whether I can express myself ok, I'm not sure.
There is an ideal parent (mum or dad) that is different for everyone, we all want/need different things.
But how many of us get it ? Has anyone got it, even ?
You recognise that you and your mum were enmeshed and that wasn't quite 'right' and I think that by asking your questions there will be a lot of answers but no one definitive answer. I can tell a bit about mine to add into the pot.
I class my mum as a friend but she is also more than that. I am happy with our relationship apart from one thing - which I find difficult to understand sometimes.
She is not really interested in issues relating to the mind (both me suffering from and studying and working in that area) - which is, like, a huge part of me.
Having said that, the qualities of a good girl friend are there - we both like clothes, tv shows, chatting. She is always there if I am upset, and I trust her.
As for my dad, a long story, but he is not interested in me. But I feel that he does care, deep down. He is trustworthy but I find conversation very difficult with him.
I find it hard to see myself as an 'adult' also, and a 'woman' - get outta here ! So much of how we see ourselves comes from what we see and hear from parents reflected back at us - its a life time journey to be you and get the relationships how you want them ( or accept them as they are and let go of yearning for what you may never get ).
Relating more as equals with my mum is definitely true for me, but with my dad it may never happen.
I feel ok talking about partners with her but I think (personal opinion only) that conversations about sex with a parent are not quite appropriate. Its ok if the daughter/son is worried, maybe needs to know about 'birds and bees' stuff. But it feels dodgy to me if a parent were to talk about their sex life with their son/daughter.
My partner has a daughter aged 18 and mild references to her sex life have been made in jokes by him - I feel a bit uncomfortable about that, but they are close and it is a healthy relationship - something that seems odd to me, cos I don't have that with my dad.
I hope my waffle makes a bit of sense, I really think its also about getting to learn what you feel comfortable with and feeling strong enough to keep the boundaries you want - this can be so hard to do, I do not want to minimise it at all. Can take years - hopefully you and your T can work on this.

nice to speak to you.........take care, Poppet