Showerthought: I walked out of a midnight showing of The Mist in 2007 and rewrote the ending in my head in the parking lot | Alternate Ending Ideas - Librear
I did the same thing after The Descent back in 2005. Sat in my car for like twenty minutes just replaying the last act in my head. The ending they went with felt like a cheap gut punch, so I came up with one where she actually makes it out and the cops find her but she's just broken. Something quiet instead of shocking. It stuck with me more than the real ending did, which probably says something about how I like my horror. Sometimes the version you build yourself hits harder because you know exactly what scares you.
Wait, you sat in your car for twenty minutes after The Descent? That's wild because I did almost the exact same thing but I was in the parking lot of a theater that was basically empty by then, just me and this one guy sweeping up popcorn. Honestly the ending where she wakes up and it was all a dream and then boom, still trapped, made me audibly go "oh come on" in a quiet theater. Your version sounds way better, the quiet broken survivor thing would've stuck with me for weeks instead of just annoying me. Tbh I feel like horror movies are scared of letting the sad ending just be sad without a final jump scare