|Yahoo messenger doesn't show the IP address of users. As you said, Only mails can be used to find the IP of the sender. |
So if you are so curious in finding about her, Ask her to send some emails for you. You can get her IP through that and the you can visit http://www.ip-details.com/ to do an IP search. This could provide the basic geographical locations such as country, state, latitude, longitude, ISP, etc. Good luck mate.