Why didn't you ask her if she liked watching 2 girls kissing? Your argument about you liking to watch 2 girls kissing doesn't apply since that is the opposite sex of you... and is probably the same thing she likes about 2 guys kissing, the opposite sex from her....
Although I have to tell you, she probably doesn't mind the 2 girls kissing as much as you mind the 2 guys kissing... it's because women are brought up to love, nurture and show affection whether it be other women or men, whereas men are brought up to not show any type of affection towards other men whatsoever.
Just like some people are uncomfortable with any type of public affection whereas some people don't mind or are slightly turned on by it... same with nudity... a lot of it depends on how you were raised... as to what level is comfortable for you.
Although I have to tell you, she probably doesn't mind the 2 girls kissing as much as you mind the 2 guys kissing... it's because women are brought up to love, nurture and show affection whether it be other women or men, whereas men are brought up to not show any type of affection towards other men whatsoever.
Just like some people are uncomfortable with any type of public affection whereas some people don't mind or are slightly turned on by it... same with nudity... a lot of it depends on how you were raised... as to what level is comfortable for you.