My wife and I recognized this problem early on and enrolled our daughter in a Catholic girls school for her last two years of high school. Her GPA immediately went into free fall. Happily, there was an older lady teacher at that school who voluntarily took charge of her and brought her up to speed.
She went on to complete undergraduate school, law school and now owns her own law practice. (No lawyer jokes, please.) I'm so happy that we had the sense to recognize this problem as early as we did and took corrective action.
Congrats & kudos to her as well! Not enough parents get as involved in their children's education as you did IMO, and too many don't know much of what is going on in the schools. I didn't know a lot of it until I saw a problem and looked into it. Not a happy experience all around. I realize not many can make such drastic 'life' changes: private schools, homeschool, etc but I would hope that all parents would put their children's needs first.