Luzzly, if your mother has learned to use and indeed manage Alexa, then why not? Obtaining wifi is easy peasy, and BT is as good a place to start as any for a first time user. Remember. When she visits you, it is already set up and you yourself are no doubt monitoring what is going on. Would you leave her in your house, alone, for a week with your system? If no, then you have answered your own question. If you think that she is ready for wifi and online interaction then can you organise some basic tutorial term?
P.S. My late lamented mil loved her online experiences however chaotic. She had many, many, family members who sorted out the sometimes unfathomable tangles that were created. She was in her late 80s and loved all of the tech. stuff. She was particularly fond of her Nintendo game machine.