Just checked up on it:
"Yes, "piggybacking"—using someone else's Wi-Fi without permission—is illegal and considered a criminal offense in many jurisdictions, including the UK, where it can lead to prosecution under the Computer Misuse Act 1990 or Communications Act 2003. It is a form of unauthorised access, bandwidth theft, and a security risk."
1. So exclude her, and when she says something, tell her you found out it's illegal - since it IS, and both of you could get into trouble.
2. Stop buying her stuff.
3 Carry on being pleasant with chats - no skin off you nose, best to keep things as good as possible with neighbours, she's greedy and maybe getting more so, but give the impression nothing has changed
4. If she alludes to the cost of the green bin, heave a huge, deeply meaning full sigh and say, so sorry I just cant afford it, so I've asked my daughter to help out.