I’m not a therapist or anything, but as your therapist brought up the emotional neglect, maybe your T could already see you were affected by it? So I wouldn’t think it means you are too much for them to handle now. Therapists are used to helping people with all different kinds of neglect, they want to help you get better. I can see how it would be scary to not know how long you get with your T, but if it’s through work can you just say you are really finding it helpful...maybe they can keep giving you sessions?
You seem to have realised so much about yourself in such a short time with your T. I think that’s great! Lots of people go years without realising anything. Is it possible to make the most of this time you have with your T, to really open up to them (in the way you couldn’t with your mother)...it could be such a positive experience for you, even if it is short term.