> so as long as the unit was legal

It wasn't, according to this article. She took a risk.

What if she was just "renting a room" and the new owner simply labelled it an "inlaw" as a legal loophole?

[Update] I didn't see the pic. Yeah, it's clearly in a different building, so an in-law.

Saying that if you change the details of a story, then the details are different doesn't actually mean anything and doesn't have any bearing on the story as it happened.

That's incorrect according to your own link:

Illegal Units are covered by rent control. Illegal units, such as in-law apartments, are covered by rent control.

Tenants can only be evicted for one of 15 "just causes." Most of these deal with allegations the tenant can dispute (e.g., tenant is violating the lease) but some are "no-fault" like owner move in or Ellis.

Not the rest of her life if the owners decided to remove the unit from the rental market.