If your friends with the opposite gender what are the boundaries or like what are the extents of a friendship

Reason I’m asking this is because I’m friends with a girl and she’s been trying to get close while I’m trying to maintain a friendship with her. I do keep a distance mentally and physically from her, but she keeps trying to get closer, I’m not sure of her religion and it’s pretty obvious she isn’t a Muslim but like I don’t want to be rude and ditch her because she’s genuinely a good person and funny and we can relate on a lot of things but doesn’t understand my limitations on a friendship. As of right now we just have each other added on socials as such Snapchat, TikTok and call each other like every weeks for couple hours but like we’re mostly just playing a game n all before it use to be non stop but I’ve sorta killed it off. A general age of myself so you can understand is that I’m in high school. What I’m trying to get at is she’s trying to commit a relationship between me and her and the signs are quite obvious but right now I’m just being very dry and slowing down because she keeps flirting with me and I don’t wanna be the bad guy and shut her down. I’m just scared if she asks me out and how I’m suppose to deal with it, If your a sister I would love your opinion on this matter or a brother who’s dealt with a similar situation like this.

If there’s any questions I’ll try to answer 🙏🏻 Thank you for helping