This post comes across as intensely fearful or hateful of men. I'm pointing that out in case it's a sign you have problems other than someone attempting to care for your mom/take your picture.

That said, I definitely support the idea of keeping tabs on your loved ones and know that long term care facilities can be neglectful (or worse). You have to be careful with nanny cams. If you are in the U.S., it may be illegal to surreptitiously record video in a long term care facility. This varies state by state - you can refer to an example here about one state mandating that it should be allowed. In other states, you need to make sure you don't violate wiretapping laws (i.e., one vs. two party consent states).

Even if it is legal, expect the facility to fight you on it. They really don't like these laws and want to cover their butts as much as possible. I've had some facilities outright tell me that they don't need to follow the laws, which then necessitated me to contact the state's department of health to warn them.

If you aren't concerned with the legal hurdles, there are some options depending on how tech savvy you are. You can get around the lack of Wi-Fi by buying a mobile hotspot. T-Mobile has one that runs about $50/month for a large amount of data. You can pair that with something like an Amazon Echo Show, but that would be a less subtle option. Sometimes the presence of a camera will change the caretakers' behavior for better or worse. Other products like the Google Nest cameras could be less noticeable.

Another option would be to enable drop-in (auto-answer) on her phone, or install remote monitoring software such as AnyDesk or TeamViewer on a laptop or tablet. These would be very difficult to notice. I've overheard many conversations because my mom forgot how to hang up and always had the speakerphone on.

I am not a lawyer so take any legal advice with a big grain of salt. Good luck - I know how stressful and difficult it can be to keep track of a loved one and make sure they are safe.