About a teenage girl whose best friend is growing up faster than she is

I am looking for a book about a teenage girl whose best friend looks like she is changing because the girl is growing up and thinks about boys and her friend is still a little girl. I don't have the title or the author. Isn't that terrible? I thought I copied it, but I can't find it. Does it sound familiar to you?

I love Book Browse for many reasons. Good reads, love doing reviews, finding books for my family and my reading group, the list goes on.. Wonderful! Thank you.

Sorry Carol, can't think of a match to this at the moment. Anyone else got any ideas?

It might be Claudia by Barbara Brooks Wallace. I think there are three by that author but it sounds like Claudia to me.

Thank you!