I would just suggest going to someplace like Staples, and sitting ;0) A chair for someone else can be so difficult. I'd had my eye on a Tempurpedic, ergonomically designed desk chair for my mother, who does need arms for rising. When I took her in to try a few, her best fit was a generic smaller chair on sale for about $85. A plus was that it was pretty with some topstitching, not revealing its modest price. That was a year ago and she still loves it.

Keeps sinking down. I bought the red racing chair with the red on the top of the arms.

I'm not going to comment on the how the color works. But as someone who has recently been shopping for a new computer/desk chair myself, I hope this is one you can try out in person to first make sure it's comfortable for hours of sitting, that it supports your back properly, and that it has a decent range of adjustments. I'm in the process of returning a chair to a local store, that is great to sit in but has weird, uncomfortable arm rests that can't be adjusted to a comfortable position for mouse and keyboard use.

Something like this may work. Choose one with a slightly wider arm rest. Swivel chairs with a high back and arm rests that are leather upholstered will be more comfortable but will look slightly more office like.