I once had a crit partner who would note every time I used the phrase "I could care less". It was a pet peeve of hers, because obviously you can care less than you already care. The correct phrase is "I couldn't care less". Problem with using the correct phrase every single time is not everyone speaks 100% correctly 100% of the time.
Personally, I've always said "I could care less'. For years I've been wrong. Now I could justify my incorrect phraseology. Sure, I already care little for whatever I'm talking about, but if it gets any more boring, I could, in fact, care less about the subject. But yeah, it's still wrong.
And you know what? I don't really care. I'm not writing my Masters Thesis for English. I'm writing fiction - about flawed people who don't have Masters degrees. Often they're lucky if they got an education at all (especially in the case of genies, some of whom were born before formal education, or in the case of a dystopian world where schooling may not be the most important thing to society any more.)
They're just people out there doing amazing things with the gifts they have. They use bad grammar and end sentences with prepositions. And they start sentences with conjunctions. They even sometimes use cliches - because :gasp: people out there in the world speak and think in cliches.
Your average dude - even the ones who end up doing amazing things - don't spend time worrying about whether their English is correct. They say folksy things sometimes and they don't worry too much about rewording a phrase because tons of other people use it.
And yet, writers get nailed for it every time. Funny.
Anyway, as a reader, I don't mind when people use incorrect grammar in dialogue - or when the POV is first person (which pretty much makes everything dialogue when you think about it - it's dialogue between the MC and other characters or between the MC and herself or between her and the readers.) In fact, I'd say I like it even better than a writer who strives to make everything so correct, they lose the integrity of their character.
So, I say, use whatever phrase feels right. And if it ends up getting someone's undies in a twist, so be it. 'Cuz that's how people talk. It ain't right, but it's more real.
(Disclaimer: If you're going to play with the rules of English, please for godsakes, know them first. Don't just slap the words down and when you get called on their wrongness, say "I meant to do that". It's disingenuous and it sucks.)