Girl has a huge crush on my boyfriend...?

[lala]

Basically this girl who's good friends with my boyfriend has developed a huge crush on him. It never bothered me till about a week ago. She started posting on his Facebook/Instagram but my boyfriend never reacted. I said to him that it made me feel a bit funny seeing this and he reassured I have nothing to worry about, he's with me and not her, he only sees her as a little sister. My boyfriend is always happy to help a friend, will always try and help and is just a nice guy! But I think him being a nice guy is what's making her like him even more.... The other week, I got my hair dyed and cut, then the next day this girl has the exact same hairstyle as me. I then bought a new dress that my boyfriend said looks amazing on me, the next day she has the same dress...I trust my boyfriend completely. He has never cheated, hates cheaters cause a girl cheated on him once and his best friend, and he has NEVER done anything to hurt me. But this girl is getting to me and I'm not sure what to do.