the reality is your girl shouldn't be frequently texting other dudes as "friends" usually it's just a roster of guys she has on deck in case you fukk up or things don't work out with you...which implies she isn't totally sure about you in the first place
if it's friends that only hit her up because old high school friends are hanging out and they are asking her to come with you because its a party thats cool
it's a case by case basis...sometimes people just like to gossip about common people they know and you can't do that with her because you don't know any of those people she knew before you came along
most of the time you can't sit there worried about it all day or you can drive yourself crazy but its all about the frequency of the "friends" contact and whats it for.