Fake friend?

Lately this summer and even last school year my friends have been leaving me out. Specially this one girl who I thought I was really close to. I met her in 5th grade because we were in the same class. We bonded fast becuse we shared similar humor. But like I said I've noted her becoming more distant. She never really reaches out to me unless I do. She'll hangout with people in our friend group and not invite me. Ive texted and talked to her about minimum four times and it's relly starting to make me upset. Ever snce I last talked to her about how I fet she's texted me once or twice first. I'm just getting sick of her constantly leaving me out but I dont't know what I should do.