Huge 'ifs':
1- if you are honest as you claim and there is 'nothing' (?)
between you and a former girlfriend
2- and if you're former girlfriend feels the exact same way
3- and if you care as much as you claim about this current
person then . . .
I would suggest you leave your current girlfriend.
Sorry. Why ? Well, you need to instill a critical life-lesson into her
and the best means to achieve this is to bring the consequences
of her irrational behavior to bear.
You are not doing this just for her either. You must also learn
to understand that unless the other person can be honest with
themselves about their negative behavior, then there is nothing
your concern and love can do for them. They must be able to
see the damage they cause, and sometimes the best way to
equip them with this fantastic vision is with the loss of said
relationship.
You need to be wary of fomenting dependencies . . . Assuming
ofcourse you are being honest . . .