i would say she is stressed out and let the babies go to early...they could be deformed but that is a sign babies are coming very very soon
A breeding tank as in a seperate tank, or a breeder net/trap? If it's the latter, take her out. Mollies are too big to really be in those things, and being in them can greatly stress them out. This isn't good for birth. And no, don't put another female in with her, she'll just eat the fry.
Mollies can give birth over a few days, but it sounds like your issue may be more stress related. Are you keeping them in salt, by any chance?
What kind of salt? If it's marine, 2 tsps doesn't seem like enough to make it brackish?![]()