Surely a valid lease gives a person a right to sole occupancy as such isn’t the act by the landlord illegal? I think the lady should do the two things suggested ie install a camera and try a bit of diplomacy.
In theory it is easy to say just confront the landlord but in practice that can turn out badly without proof. If the lady has video proof it will help if things turn nasty.
Certainly the diplomacy route should be tried first and the angle of ‘safety conscious’ is a great way to broach this.
If the lady gets video evidence it should make her a lot more comfortable about asking for her rights to be protected. She doesn’t have to use the video. Last time I checked it wasn’t illegal to video in your own house (which is what a lease means).