Spoilers!
I think a lot of people got confused about Brian and Tina's relationship. Most thought that Brian was trying to "make moves" and flirt with her after his brother/her boyfriend was killed, in which is kind of wrong.
Not true, at least I thought so. Brian was just trying to befriend her and gain her trust because her father may of had a link to his brother's death. Moreso, Brian also tried giving her some closure to the loss of her boyfriend. Even when Tina went to go visit Brian in the hospital he clearly stated he'd be a friend she could rely upon.