Definition could be a bigger thing.

I used my son's HP Chromebook for about a year as a third device, and the screen was indeed pretty bad for reading.

Tuning brightness, colors and bumping font sizes helped; but at the end of the day it's a very low DPI screen and intricate letter shapes are that more blurry at the sizes that were easier for me to read.

I have no trouble reading all day on a Surface Pro, for comparison.

I could not figure out a way to extract a pdf of the textbook to send to her kindle. I would have liked that solution, since she has one of the large format kindles.

I used to have PDFs on my Kindle, you used to be able to email them to your Kindle, I think Amazon killed that functionality, I believe you can plug it to your computer and mount it and drop in the PDFs but I don't know if it needs to be in a specific directory, just be weary of image heavy PDFs they may not load at all.

I do know how to load arbitrary PDFs onto the kindle, you can do it now with a specific email address that's assigned to each kindle. It's allow-listed for coming from your amazon email address though.

I was not able to extract the PDF from the online textbook. I think I had something that would have worked to just get the content, but I'd have had to stitch all the chapters back together, and if the page numbers didn't match the original book it would have been a hassle for my daughter.