I see a LOT of this kind of thing, but the top comment thread on this AITA post really summarized it well.
Gaslighting is when someone argues with you about objective reality. Not about their opinions.
https://www.reddit.com/r/AmItheAsshole/s/YWQAskNBTg
So saying “she doesn’t hate you, she just has depression/is prickly/doesn’t explain herself well” is not gaslighting. Depending on circumstances, it could still be a douchey thing to say! But it’s not gaslighting.
