Silent Pisces Girl?

I met this pisces girl through a friend, and we all often like to talk. She's a really talkative person around him and other friends, but when it's just me and her, we tend to usually have this silence, where she looks on her phone and I'm just here thinking what to say, because I try to spark up conversations, and we talk about it for a little before going back into silence. She did accept me into her friend circle early on though, and became a sort of "parent" to me. We've been friends for months now.

I'm just wondering if it's just that I'm just not interesting to her, if the other friends were just really "aggressive" in starting conversations, or if it's something else.

(I'm also a Pisces if that's any indication.)

Maybe she's not 100% comfortable with you yet. I'm a Pisces my self and can be silent to those i'm not used to yet. Get her to laugh, or no matter how hard it seems try to keep the conversation going.