My daughter, I'm worried.

My daughter has gone out to an old friends house and I am worried about her. This so called friend is really mean at times and when my daughter used to live with her, for 8 months, she did some really horrible stuff to my daughter. She wouldn't let me stay with them when I came out here for a holiday last year and said the only way I could stay with them for a week is if I pay rent to her. She wanted to charge me $100 a night, just like it would cost me if I were to stay at a motel. So I didn't stay and my daughter moved out because of it and now I live here too, and we got a place together. When my daughter moved she threatened her that she was going to beat her up so my daughter had some people help her to move because she was scared of her.

Now she hasn't talked to this girl for about a year, till today. The girl emailed her and asked her to come over and hang out together and my daughter just left and went to her house. Now I sit here and worry that this girl is going to beat her up. Why did my daughter go, you might ask, I don't know. I asked her the same question, why would you want to go see her, and she said the girl is sorry for the way she treated her and wants to be friends again. I don't trust this girl and I asked my daughter to phone me and let me know she is okay, later. She, my daughter, thinks I am being over cautious, and I hope so, but how would my daughter know this girl is on the up and up and even if she is, why would she want to hang out with her?

Am I just being over protective or am I right in this? My daughter is 25 years old and I guess she can take care of herself but she is a little too trusting and it has gotten her in trouble before.