If she doesn't realise how much of a roller-coaster her words and actions are sending you on then she has no business using them.
You can be reparented in therapy to an extent. But reparented doesn't mean you get to be a little girl and you get your dream mommy and you both go play-act shopping trips and mother-daughter moments. Reparenting in therapy is a really poor substitute for what it is you really want in your heart.
Reparenting if done right, can be very healing but it is all done WITHIN the confines of therapy, within the therapy room. It has limitations in that it can only respond to the parts of you that haven't been able to grow up emotionally and a compatent therapist will meet you where you are emotionally and respond in a healthy consistent way to let those parts of you learn and to grow up. It's not about rewriting history.
Your therapist/case manager is really not being clear about what the boundaries are, what the therapeutic reason is for going shopping with you- you are an adult and perfectly capable of going shopping for yourself, what was her role there? She's allowing you to indulge in this fantasy that she can be your "other-mother" giving you false hope, while at other times towing the therapist line about boundaries and bringing it all back to a therapist/client relationship and nothing more. Very confusing and very unfair.

You have a mother. She might not be a very good one, and clearly she has her own issues but a mother who doesn't care doesn't financially support her daughter thru college, doesn't advocate fiercely for what she thinks is best for her daughter (even if she is wrong and abusive or whatever is going on with her) let her 20 year old daughter come home, a mother who truly doesn't care kicks you out as soon as possible and has nothing to do with you. On some level no matter how screwed up she is, in her own limited way she is showing her love and care for you.

I'm not sticking up for her when i say that, i think she's done terrible damage to you but it's not black and white, there are shades of grey. And she thinks what she's doing is out of love. That's what mothers do.

No therapist will ever come close to fighting for you the way a mother (abusive or not) will. No therapist will ever fill that hole you feel inside, in fact no human will ever fill it. The only person that can do it is you. It becomes filled once you stop frantically avoiding the work that needs to be done, and find the acceptance that you had a crap childhood and have a crap mother. Once you face that, then you can begin the journey of grieving for the loss of it all. And the more you grieve and accept and practice self-care, the less that void becomes. You have a lot of hard work ahead of you, but it will only start once you stop looking for a new mommy and stop avoiding the real loss.