D.E.
If she is drinking/eating a lot of juice, fruit or sugary things it can cause the teeth to rot and bad breath. Also, if she is going to bed/nap with a bottle of milk or juice (anything other than water) and falling asleep with the bottle in her mouth, then the liquid is basically sitting there and fermenting in her mouth. That could definately cause bad breath. If it's not something simple like this, I would try a dentist. But if she is still swallowing the toothpaste (which I imagine she is at only 15 months) ask the dentist before upgrading from the toddler kind.
(Mom of a 24 mo. old boy w/lots of young nieces and nephews)