If the SD card is empty then nothing was being saved to it. You often need to change settings telling the phone to use the card. Like the camera, by default saves to phone unless you change the setting.

One thing I suspect is the memory card reader may be working. Personally, I’m surprised when they do work. I would try another card reader.

There is no indication that her email has been has been compromised. It is still recommended the password be changed to be safe. Then check her credit card transactions to see if there is something she doesn’t recognize.

I have several routers. Except for the isp proveded one, they’re all second hand.

Technically yes, but realistically, no. I wouldn’t think twice of buying second hand equipment and many in the tech field would encourage it. However, if you are paranoid just reinstall the operating system. This would disable any hidden software they may have added.

Standard scam. Sounds like you stopped before letting the person. You would have to enter the address and download some sort of connection software. Then open the connection software. Sounds like you stopped before doing all of that.

I would reinstall using a thumb drive. I wouldn’t that the virus is still present, just a corrupt installation.

“Create Windows 11 Installation Media”
https://www.microsoft.com/software-download/windows11

I would first just try moving it around. Sounds like you have a wifi AC(5) router which is still very capable. But a lot of things can interfere with that signal. If you have a long enough cable move it into another room just for testing to see if your speeds improve. If they do then you know its the location.

What’s the model number printed on the box

The hackers got into what software?

If he can get into the account he should be able to change the email back.

I have a feeling this was not explained properly. By chance do you mean that when he logs on to windows his files are gone? If so I would first think it is a corrupt account, which is common. The files are there but it takes a bit to fix. This is just a guess with the limited info.