We have a thread for Mass Effect discussions, but I will answer your question here. First, the link:
http://gamrconnect.vgchartz.com/thread.php?id=114628
Relationships in Mass Effect tend to be heteronormative. Conversations for homosexual relationships were recorded in both games, but you have to mod your save file with a save editor to get them to show up. That only works on PC.
As a female Shepard you have to romance either men or Liara, the blue mono-gendered alien lady who can be romanced by either gender. The selection of romantic interests in the first game for either sex comes down to your opposite-gender human party member (Ashley and Kaidan) or Liara.
In the second game it branches out a bit, and the female romances become a lot more interesting and better-written.
