I don't think I can do this...

I adopted a Beagle from an animal hospital a friend works at. She is estimated to be about 9 months old and seems to have some training. Things were fine, but now so much. I have an older dog who doesn't like her. He has stopped eating and doesn't want anything to do with anyone, just wants to stay outside. He seems as if he is depressed. Roxie (the Beagle) is using the bathroom on the floor, even after having been out. She has bit me twice and won't listen. My younger brother is allergic to long haired dogs (our older dog is short haired and he is fine with him) and Rox is very similar to him, but my brother has been having allergy problems since bringing her home. To top it all off, I think I am allergic to her as well :/ I was fine until after being around her for awhile. We have only had her a few days and it's just one thing after another. I don't know what to do or if I take her back to the hospital how that will work out... I don't know, all I do know is I don't think I can do this and I hate that can't :/