Why does my friend compete with me?

My daughter is 6 and she is in the same class as my best friends daughter! Everytime I do anything or go anywhere she copies me! She told me her daughters reading books are higher than my daughters and she tells me everything she buys to try and go one better than me! I feel like I'm having to keep things to myself just to stop her copying me! i.e I bought my daughter a flute so she can start learning and I have had to tell my daughter to not tell anyone! I've also booked her birthday party and I've had to tell her to keep it a secret till I've done tge invites just uncase my friend steals my idea! I really want to tell her that I'm flattered but it's too much but I don't want to hurt her! She is just about to move house and it needs alot of work doing to it but I've been really supportive cos I can see it's upsetting her but I moved recently and my house is all done! But she seems to be copying my taste there too! I don't k ow what to do! I just want to be individual and for my daughter to not have to lie about stuff she has!