I have used a Zoom 5352 modem with Xfinity TV and internet successfully in the past. It was always on the list of supported modems. I gave it to my daughter to use (internet only) and it typically works fine, but service becomes intermittant at times. Is the Zoom 5352 still on the list of approved modems (I can't find the current list)? If not, what does that mean? In other words, will the 5352 still WORK, but if there are issues, Xfinity will not help troubleshoot? Other sites (Amazon, Zoom, Best Buy) indicate the 5352 is approved by Comcast.
You will always find a current list at https://mydeviceinfo.xfinity.com .
Browsing that list, however, I don't see that modem, and given that it has a built in Wireless-N router and only 8x4 download channels, I suspect it's been phased out for obsolescence. She's going to be way better off with a newer one that has better speed, reliability, and security.