Children are always comparing themselves to eachother these days. In the old days most kids just had dirt, a creek and a fishing pole to entertain themselves. Now the sky is the limit with toys,entertainment and the latest style of clothes. Try to nip it in the bud while she is young that "stuff" equals popularity or happiness& fun.
One day recently our oldest said to me "Mom...I want to live a life of luxury!!" It was said while he was in a giddy and funny mood but I took the time to set the record straight. He is a very compassionate and nurturing boy and I tapped into that. I reminded him of all the many blessings we have of food,beautiful home with pool, toys, school down the block, health, freedom of speech&religion etc....It was not so much a preachy speech but just to drive a point home. He quietly said, "Ok Mom...I get it..I guess I am living a life of luxury already." I hugged him and we talked about the "wants" he has and how friends seem to have sooo much more. I told him I felt the same way when I was younger.
Soooo, keep encouraging friends coming over. Do some activities with them..they will love it. Paint, playdough, plant some flowers in paper cups and send them home with the friend(she will be thrilled!),make cookies together and send some home with the friend with a recipe card and note that says, "Look what I made with my friend_________!".
My kids love having friends over to hang out and play. Recently my my son and his garage band were over..he asked "Mom,can you give us the royal treatment?" I asked what that meant. He said, "You know, bring us snacks and drinks and stuff." Sooo, I did and it made him feel so good to share goodies with his friends. I didn't know juice and crackers equaled "royal treatment" but I guess so in his mind.
Good luck and best wishes!