Well, as you know, that push/pull love/hate thing is part of what you deal with with your BPD, and if I remember right one of the skills taught in DBT is distress tolerance. No one can be 100% consistent 100% of the time -- that's inhuman -- so being able to accept a schedule change (relatively minor in the scheme of consistency issues) is probably a place to start.

Something to think about that struck me: You might also need to be aware of your own need to stay consistent and provide consistency within yourself with this T by not running when you feel any discomfort. You did good work going back and communicating your discomfort with the schedule change. The trick in the future is to voice that first to prevent the whole going on another T hunt drama in your life. Just think about how much less stressful your week would have been if you had voiced your concern in the moment and worked through it with her then and there. You have to create that consistency within yourself so that in those times those around cannot, you have yourself to fill that gap.

I do think she may be exactly the T you need right now, and I hope you'll continue to make gains while working with her. Glad it is going well.