I'm starting to suspect that my sister is gay

I came out to my family a few weeks ago, and my sister's reaction was the only truly negative one. Immediately after I told her, she told me that I was just confused and that she didn't think that I was gay and that if I came out to my parents, horrible things would happen. Later, when everything had calmed down, she told me that what she said were "exaggerations", which, given what I know about her, I doubt. She also told me that when she was in high school, she was afraid of being gay because of all the problems that it would cause and whatnot. She's had a lot of boyfriends but not a lot of serious ones, if any. She never seems that into the guys she dates. She also dates a lot of terrible boyfriends. She has told me that gay sex isn't the best kind of sex, and the thought of doing gay sex horrifies her, while straight sex turns her on. Despite claiming to be "liberal" and "having a lot of gay friends", she's the least accepting in my family, including my conservative father. When I mention that I find a girl hot, she gets very uncomfortable and tells me I shouldn't because the girl is probably straight.

Her behavior confuses me. I'm wondering if she has all of these preconceived ideas about being gay because she might be questioning and for whatever reason can't handle the idea of being gay herself. I don't know. Am I overthinking this?