Lag was certainly a factor, but there were also weird behaviors like visual glitches and UI rendering issues. There were a number of intermittent problems that are hard to list specifically, as it’s been a few months since we tried it.

She is not a power user. Working inside a container running Windows just to display MS Word introduces complexity. separate file systems, etc. Sometimes the abstraction breaks, and you "fall out" of the app and end up staring at a Windows environment. It is very confusing for a layperson. On top of that, the RAM overhead was significant for her older laptop.

She is a kindergarten teacher. The last thing she can use is friction on her laptop.

We didn't try LibreOffice. I'm familiar with it, but the learning curve/transition is just too much friction. They also share a lot of documents with colleagues. I don't know the current state of compatibility between MS Office and LibreOffice, but I recall layouts breaking regularly. She also has a library of templates originally created in MS Office.