F19 I’m so confused

I think my older (f21) sister found out I’m lesbian though I don’t know if she is. she asks me normally what I think of her outfits and such if she looks cute etc. but this past week it feels like she is teasing me. she’s sent me some pictures of new underwear and bras that she got askinf if they look good. and she poses In ways that have been turning me on. I’ve never felt like this and have been mostly eh like she’s my sister but I’ve seen pics of her nearly flashing me. the last one she sent was like, “I bet you like this one“ it was a mirror pic but her bra was smaller and her finger was pulling her panties down a bit. I told her she looked great but it made me so wet and I couldn’t look at it. idk what to think and I’m wierded out idk what to do. like ive been sent pics of other pple sisters that I’ve totally Gooned to but this is new. and I think I like it but it’s my sister ew