7 year old teenager

Kendall, oh my.  If this is how she acts now, heaven help me later.   {she’ll be 8 next month}

She is snappy with everyone, she gives me the snottiest answers sometimes, she acts like whatever I say to her is RIDICULOUS.  She stomps around, throws things {she threw Evan’s phone at the pool a few days ago, after I told her her friend could NOT come over because we had plans that night…and BROKE IT, he had to get a new one, luckily he was due for a free update}. 

She stays upstairs alot when she is home, in her room or watching TV in our spare room upstairs…
Like now, she just got dropped off, she was at Bible Camp with her friend…and went straight up stairs {she did say Hi to me and Raji, and snarled at Evan} and is upstairs watching tv & I won’t see her for hours.

She also spent the last TWO nights at her friends house.  When her friend asked her if she wanted to spend the night & I said sure…she just said OK! and was out the door & off… didn’t even say BYE or LOVE YOU…. she doesn’t care!!!    She didn’t miss us at all .

When did she get so "grown up"??? And how can I make it stop.