I do that all the time. What usually happens is she is meaning to get off, but someone else IMs her, and yeah...I wouldn't worry about it until she starts signing on and doesn't say sh!t to you. Then, you'd have a problem.
Who knows...she might...but then again she might just want to "bling bling" with your chains.
The best thing to do is ask her, or if you are too shy, have a friend ask her.