Help!

So me (22m) have been with my gf (21f) for almost a year. We have had a really good relationship and we are strong together. I enjoy spending time with her and we have so much planned for the future. However, she has been snapping this boy before the start of our relationship, like way before. They were really good friends and used to do work at the library together while in college. I’ve always been fine with it but they have this super long streak. That they have to keep. I think it’s a pretty weird thing as they literally only send pictures of there face now to keep it. I’ve said to her why do you keep it and she never gives a solid answer. I think streak were cool when we were like 13/14 but she’s 21 now so I’m starting to think it’s pretty weird. Also she will never open the messages infront of my even tho she opens everyone else’s messages and if she does open in front of me she will turn her phone. Plus I’ve questioned her on this and her reasoning behind it is it’s just gonna be a picture of his face. But why can’t she open in front of me. We spend a fair bit of time on our phones and through your whole relationship I’ve seen her reply to one message of his asking to meet up and do work at the college. They have a streak of like 800+. I’ve always been an insecure person so I’m not sure if I’m thinking too deep into this. She says she’s not even friends with him anymore so would I be in the wrong to ask her not to have the streak anymore. She says she’s never seen him in more than a friend way but I’m not sure if I truly believe this.