I know I said I’d stay out of it, but I’m a mac user, and I’m hoping I can help.
New imac displays are shipped optimized for web viewing using RGBs color profile, just like the iPhone and iPad.
So I doubt her gamma or color is off by much if at all for web viewing. Even after calibrating I hardly noticed a difference at all. Ok seriously, my eyes noticed no difference. (Changes were made, but… Maybe I’m whack, or maybe Apple kinda got things right?). I think this may be more about her eye than her monitor.
The color space in which you work depends on what your photo lab specs are and/or your printer, and how it’s calibrated, and also what color profile they calibrate their printers to, and if you wish to preview how your image will print on certain papers/products and their profiles (the preview/proofing is close, but not exact as there’s no way to make a screen behave like paper). I usually work in a color space optimized for web viewing, and make a duplicate image worked in a space optimized for a standard print from my lab on my preferred paper. When using different papers and products, I use the color profile provided for each for my print proofing. I also sometimes dim the brightness when needed to proof prints. Mac displays are notoriously bright.
This link will help get you started
This all does make me wonder though… How long have you gone without printing or making finished products for your clients? To me, making photographs was my logical first step as soon as I decided to start taking my hobby more seriously. Color managing (which goes beyond just being calibrated), I learned the hard way by thinking I could just send a file anywhere anyhow and get back what I expected. OY! What a nightmare. Months of torture and craptastic prints lol
Color managing can be a bit of a complicated nightmare at first, but once you get a good routine going it becomes second nature, with maybe just a few hiccups here and there.