DD. The danger it from malware … which comes from malicious users … and can infiltrate a router’s security and infect all devices which share it.
Yes, a guest network, if someone knows how to set one up, will reduce the risk of malware attack but it can’t prevent a guest (or their guests) from visiting malicious websites on their own devices … which will still register to the same public IP address, as all internet traffic is routed through the same ISP connection.
So were they to do something illegal it could still come back to the person who has the contract with the ISP who, as I said before is likely to be be in breach of their contract anyway by letting the neighbour piggy back.
We are going down a tech rabbit hole when all OP is asking is whether she is being taken for a mug … and she is.
Leaving aside the dangers of network sharing, the neighbour is potential saving say £20-£25 a month in broadband costs while OP is saving probably about £60 a year for green waste collection.
To OP. I think I would be inclined to say that your Internet Service Provider has recently updated their Terms & Conditions which you took the time to read. You can say that you hadn’t realised that you weren’t allowed to share the internet connection and that the arrangement will now have to end. Give her a couple of week’s notice so that she can organise a broadband installation and then change your password. (If she drags her heels, change it anyway.) The neighbour may just accept the change and let the green bin sharing continue. If she plays tit for tat then you have your answer about meanness.
It’s worth pointing out that there are reductions for green bin collection costs for people who receive council tax support as well as broadband social tariffs for people on low incomes.
