Are you sure you have to choose? Maybe in your case more sources of support would work well and I have understod your T has even told you you need more people to depend on, not just her? Maybe that is something you could ask both your T's next session, she might not be against it at all, whatever the rule is. You do worry about lots of things, maybe taking one day worrywise at a time could be something to aim for. We have no way of knowing for certain how things turn out in months. Maybe then you want to choose one or another. Your situation actually sounds really good - you found an interim T you seem to like a lot. How could it get any better now? I'm happy you found a great T to work with.