It's hard when we so identify with other people that we lose sight of our own boundaries. I would take your T's advice and leave this particularly girl alone for the moment, until you are more centered in yourself and can be sure of a bit of detachment when with her. I think it is very exciting to imagine getting ourselves fixed as we help another with the same problems but there are too many unknowns; if we could have fixed ourselves before, we would have done it before? And things that don't fit the pattern could come up while we're working and swamp us as your T says.

It can end up being very close to a folie a deux? http://en.wikipedia.org/wiki/Folie_%C3%A0_deux