How to handle a letter my 8yo got

My 8yo is best friends with a girl we left behind when we moved.  They write letters back and forth all the time.  Luckily, Lydia lets me read all the letters (mostly because she has trouble reading her friend’s writing).  She just received one that I purposely skipped over parts…  It was about Big Time Rush, who her and her mom got to see a little while back.  She went on and on about the band and all the guys in it, including info about their looks, their “time with the gals,” and their trouble they’ve gotten into.    I explained to Lydia why I skipped over parts of it, and she was perfectly fine with it.  She was pretty bored with the letter, anyway.  Not only did she not know who the band was (thank goodness!), but she really could care less about the music industry at all.  Now, though, I feel I should talk to her friend’s mom about this.  They are Christians (the girls met in our church’s preschool).  Her mom and I are fairly good friends through FB, mostly, and I’ve helped her out with a few things.  She does come to me for advice, so I know she trusts me.  I just have no idea how to bring this up to her or what to say.

Any advice or thoughts on this?  (And my hubby wonders why I think private school can be just as bad as public school!  )