Video chat with leopard: iChat to AIM

I'm using iChat4.0 and my friend is using AIM 6.5 on vista and when she is connected through the wireless network at her school, there is the icon to video chat with her and it works great ,sound is clear and picture is crisp. The problem is when she is using the ethernet, there is no longer an option to video chat with her. Anybody have any idea how to fix this? Thanks.