I've heard that a good way to acclimate them to epsom salts water is to premix a gallon of epsom salt water and then do 25% water changes with the premixed treatment water every five minutes for a half hour. You will probably have to mix up a second gallon of epsom salt water, but its not that hard. Make sure all the salt is dissolved before you use it, and make sure the water is the same temp as the tank water. I don't know anything about bettas except what I've heard from other threads about them, but this is what you do with adult bettas and I'm assuming its safe for babys too. I've heard that newly hatched baby brine shrimp are good for baby bettas, that probably hard to get though. Heres a link to a website about breeding bettas and taking care of the baby bettas. http://clefty.hubpages.com/hub/bettafry
Of course, the experts would really know better what to do, but I hope this helps, she's soooo cute. Good Luck!