Oh my gosh, noooo. No reason for her to be flirtatious with you. I am sure you didn't imagine it, and with no other support structure, I can't imagine how devastated you feel. Having feelings of arousal would be oh so normal too! You have developed all this trust with her and you have the right to expect her to keep appropriate boundaries! Even if you had transference feelings, it is up to HER to control her feelings and keep things healthy and therapeutic.
You expressed concern and even cancelled sessions, she denies sexual feelings and then acts seductively towards you again..... I would trust your instincts and find another T. I know how horrible that feels but if she can't control her behavior, I really concerned for you. What is going to happen if this relationship turns sexual? Is she going to deflect responsibility onto you? Sounds like she is ok with denying and lying about how she really feels. Take care of yourself and know that you have no reason to feel ashamed or blame yourself.