Biking on sidewalks in Cambridge? (Broadway and Harvard)

Stressed parent from Montreal here whose young adult kid just moved to Cambridge. She tells me she is going to bike to work (8 mins, vs. 25 min walk). She *never* biked in Montreal because she found it too dangerous because so many bikes were on the bike paths. (The bike path by my house sees 10,000 trips a day, so the speed and number of bikes put her off BUT it is separated from cars by a concrete median so I consider it safe.) Now this newbie biker wants to ride in the narrow streets of Cambridge. The bike paths that I can see online seem to disappear at random points, and anyone on them can be doored at any time. I looked at the regulations for Cambridge and realized she could get to work riding on the sidewalks, which according to the city website, is allowed (not everywhere, but many places including Broadway and Harvard). Do people do this? Will people yell at her? I'm trying to give her alternatives that won't risk her life, since I don't want her to find out by experience that the real danger to cyclists is not other cyclists, it is cars.