[lily's mom]

I have a little problem. My 9 year old daughter has an overnight guest over. Lily has been going nuts barking at her since she got her. (Which is normal for Lily to do to everyone)
I Thought, geez, can't do this all night so I slowly introduced Lily to the little girl and everything was fine for about a minute. Then the little girl starts to get up an Lily goes bizerk again. Lily is outside and the little girl is crying. What in the world do I do?