When I look at some of the routers they have six antennas, etc - but do you need that for a dorm room?
No, a two antenna, or even a unit with internal antennas will be fine, since such a small area needs to be covered.
What should I be looking for in terms of specs? Wifi6?
Definitely AX, because of the phones, and more available channels.
Or does that matter? Is 2/3 antennas enough? Anything else I should be looking for?
Like many here, I am a fan of Merlin Firmware, and then an Asus router to run it.
I don't think that is what she needs.
I would recommend a low end AX router, like one of these from TP Link:
We’ve tested the latest Wi-Fi routers and found the best options—from budget models to top-of-the-line—to make your wireless network faster and more responsive.
www.nytimes.com
The AX 50 at $100 is fine for a dorm room. Note: if you set it up for her, just shut off the 2.4 ghz band, it's going to be worthless in a dorn, and set her 5ghz band to a high channel, or low, not in the middle where DFS is an issue.
The AX20 from TP link, or the AX10 would also be fine.
Links to the AX20 in that article, AX10 here:
https://www.amazon.com/dp/B07ZSDR49S/?tag=snbforums-20
Ha! Amazon shows that i "Last purchased Sep 1, 2020". it was a gift for someone, it's still in service and has worked fine for them.
Even that one would be fine at $70.
Also good and solid over the years:
https://www.amazon.com/dp/B079JD7F7G/?tag=snbforums-20
Fifty three bucks.
This was Wirecutter's recommendation for years. It's AC only, but it's going to be enough for a student in a dorm room.
If the student has a TV/console/desktop, need to get her ethernet cables so she can hard wire that or those devices. Anything that does not move needs an ethernet cable. (Dorm airwaves going to be pretty busy I would guess.)
Again: don't even try with the 2.4 ghz band, in her room, 5ghz is perfect, and ideally on a channel that is not saturated. In busy environments, I like to hard set the channel, not set it to Auto, and let the other routers in the area find a channel that my router is not on. (If that does not make sense, let me know....)
Good luck and that you for helping her out!