My girlfriend is adamant that her sister has a crush on me, but I think she's just being friendly. What do you think?

My gfs sister is a bit of a loner, I felt bad for her so started inviting her over to help me with a few projects, repairing cars etc.

I'm 26 and her sister is 17

for the last few months my girlfriend has been getting upset with me, asking me to cut contact with her sister because she's adamant that she has a crush on me. But I don't want too we get on well and she has a great time.

The Reason girlfriend thinks this is because, her sister acts completely different when me and her are alone she smiles and laughs (flirty laughing apparently) a lot when she's with me. for context she's very quiet normally even with her mum and sister.

She's more playful throwing snowballs etc. she also stares at me when I'm not looking and always tries to sit right beside me which I haven't noticed. she talks about guys who ask her out but she rejects. She opens up about her life struggles in general.

I don't think she does have a crush on me. think she just likes having a role model

What do you guys think?

My girlfriend is adamant that her sister has a crush on me, but I think she's just being friendly. What do you think?
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