I've never been in that situation, but if she's biting when excited maybe you could talk about other things you do when your excited? Maybe a silly dance/clap hands/cheer? And then next time something good happens make a big deal out of doing the silly dance together? If she bites maybe just calmly ask what we do instead of biting, because biting hurts and isn't respectful. I think your doing a great job in a tough situation!