I agree with Brittanagleefan and freffy123...just because you're in 사랑 with a girl doesn't mean you're a lesbian and she did say in the episode that she was attracted to both guys and girls.
BISEXUAL/PANSEXUAL. I think many of these 답변 are misinformed about bisexuality. Just because she has the strongest feelings for Brittany does not mean she is not attracted to the opposite gender. She seemed to like Puck in the past, and was physically attracted to Sam. She said she likes boys and girls. 호랑 가시 나무, 홀리 didn't say anything about her being lesbian - she only asked her if she was. Based on Santana's 설명 of her sexuality I think she may be pansexual. Santana also called Brittany "fluid" - sexual fluidity is another way of referring to bi/pansexuality. I'm pretty sure they're both bisexual.
What we know from this is that Brittany is the first person Santana has experienced anything 더 많이 than physical attraction to.