Anyone experienced this?
Not an adolescent, she's about 7 years old!
First I had to ask her two or three times to lie in her bed (normally only have to ask once!).
Then on a walk she decided she wanted to go to the woods, ran miles ahead and refused to come back when called, just sat there waiting for me to get closer then ran off further 
The absolute worst was a few days ago, I let her off lead (as normal) and she ran off!
She has never in all the years I have had her ever gone out of eye line. Ever.
Even during the woods incident I could still see her clearly, just ahead of me.
This time she properly ran off, I had no idea where on earth she was.
Thank god some nice person had managed to catch her.
That one she'll come to regret as she is now harnessed everywhere except big open fields where previously she would have been off lead the entire time.
And just now, we have just come back from a McDonald's trip with the kids, I looked just by chance, to see that she had taken my DDs hat off the stairs and was chewing it, immediately shouted leave which she did, but then tried to chew it again a further two times?!
What on earth has got into her??