Oh yeah, I’m familiar with くれる: that group of verbs was probably my greatest nemesis while studying Japanese at uni, ngl. I’ve definitely heard 分かってくれる being used when talking about other people understanding the subject of the clause (often with a sort of emotional/dramatic feeling–like, “Why can’t you understand me?!” or “At least you get me”), which is why I interpreted it that way, but it definitely doesn’t mean the other interpretation isn’t possible or even likely!

…alright, I was going to just leave it there, but you sparked my curiosity, so I went ahead and grabbed a mirror of Kitsunekko and did a simple grep for (分|わ)かってくれ to see what kind of contexts it’s used in. Here’s a random few where I happened to have the video on hand with English subs (far from infallible, but saves me the trouble of making my own clumsy translations and they all seemed reasonable to me).

A sample size of three is far from conclusive, but the three I happened to grab all had the more straightforward conclusion, for whatever that’s worth.

Also I hope this doesn’t come off as trying to own you with facts and logic, you comment just made me think about how I could try to understand this better and the idea of searching anime subs popped into my head! I never found individual sentence examples super helpful because they can only give you so much context, but having fully animated and voice-acted examples from series I know makes things way clearer. There’s no way I’m the first person to think of this (sure enough, I just googled it and there’s a fancy web app which will do this for you much more effectively (albeit only with audio and screenshots), but thanks for giving me the idea!