Proper colours can mean slightly different things to different people, though if she is not a filthy apple user then that makes life marginally easier. I will assume we are going in for big boy proper colours and not just 99% of the way there on some random monitor (occasionally you get a good one, or a good batch), though many of the players here will have a "might as well be a graphics design monitor but we are not calling it that" model -- see something like the . I will also skip the testing and calibration stuff as that gets really fun.
For cheap, especially if you are going second hand/refurb, but solid screens of proper colour replication I actually quite like Dell's efforts here.
https://www.dell.com/en-uk/shop/monitors-monitor-accessories/ar/4009?appliedRefinements=2839
Ultrasharp (older and current, though not all things with ultrasharp in the name will come sorted out of the box) and premiercolor (more recent) being choice terms to search for. Say what you will about their home computers and cheap laptops (I certainly do) but when it counts for stuff like this then they do well.
https://www.tftcentral.co.uk/reviews.htm
Their reviews of the pro monitors are what you are going to want to be able to find in other things for this.
Reasonable example to start with
https://www.tftcentral.co.uk/reviews/dell_u2413.htm#hardware_calibration
Another link you might as well have
https://www.wexphotovideo.com/monitors/#esp_category_pg=3 . Some on there are the "really close but we are not calling it pro" things but others are actually pro stuff, usually reflected in the price, and even one of two "we run a lab" type setups