I'm sorry your therapy has gotten so complicated and your T is having trouble helping you work through it.

I'm very fortunate to be with my therapist, who also has a Marriage and Family therapy background, but who embraces the transference with a great deal of caring, sympathy and empathy. She's really met me right where I am and made therapy a welcoming place for me to feel mothered. By mothered I mean:

Giving hugs when I ask for them (virtual hugs because we're doing distance therapy, but she says she gives hugs in person too as clients request them.)
Occasionally reading me stories or poems so I can listen to her voice for comfort or to help with anxiety
Telling me how proud of me she is when I make progress in therapy or life (doing better self-care, speaking up for myself, graduating college)
Consistently being there for me, whether I want to talk to her evenings, weekends, daytimes
Telling me she cares about me deeply when I ask for reassurance.

You asked how we deal with it- well, she encourages me to share all my feelings, including those transference related ones. Many of them are maternal transference, mostly positive, others more complex, and we discuss them as needed, both the source of them, and working through the pain, as well as her trying to meet my requests as best as possible. It was more prominent last year, and now that we've been doing this intensive therapy for most of 2.5 years, we really don't need to talk about it anymore, though I can whenever I want to. We did several sessions a week the first 18 months, and now 2 per week, so.. it moved pretty fast.

I will say, I don't believe this type of... this level of engagement in the transference is an everyday occurrence, though I do know a lot of practitioners do believe in this general type of work, in therapy as a limited corrective experience for difficult parenting situations. And many, from different schools of therapy, that embrace transference work to give insight into a clients issues, which doesn't though, mean fulfilling the clients desires for the relationships, but just accepting the transference more purely as a learning/insight tool.

I'm very glad to be in a place where I could establish the relationship with my T that I have, I think it was a unique combination of circumstances that made it possible.

P.S. I really don't believe there is an established, agreed-upon "should" as to exactly how a therapist should handle transference, so... I wouldn't necessarily... go into it with certain expectations. There are lots of different opinions on it, from... ignore it, quash it, examine it, embrace it, to making it the all-encompassing focus of therapy and variations on those.