Hello Sofasofa,
If you dont care for any fancy features maybe you should try yahoos web messenger :
You will find it located here : http://messenger.yahoo.com/?i=1
1. Scroll to the end of the page
2. You will see a link that says Launch web messenger click on that. (If you have a pop up blocker when you click the link don’t forget to press control C while clicking the link) Also, I suggest if you use the web messenger, you might have your g/f do the same.
Just to see if it helps you both. If you are still experiencing lag time, it could be another problem.
Hope this helps 🙂