Wait, so her trauma is getting stuck in an oppressive party, getting worked to exhaustion, and then left behind? I mean, that's bad but... Is that it?
This is more or less the tale of anyone stuck in a black workplace that many isekai tales start with (before the isekai starts). It also doesn't explain why everyone around her would start avoiding her, it would make sense if she was attacked and violated, but if she was simply worked to death, you would think that would make people more protective/helpful towards her rather than to shrink back in fear that their existence alone would somehow spark trauma flashbacks. It seems that everyone sees her as someone so fragile that she can't handle normal human interaction outside of semi-scripted events (work/shopping/etc).