@JurassicSal Eeek, what an awful situation. And it's not going to get better, until you move - or SHE moves or shuffles off her mortal coil.
It's a bit of a cheek - and wrong - to regularly depend on others. It's so unfair, as many people have their own set of responsibilities, including life admin, family, home, chores, job, and F knows what else...
And some people in their 40s, 50s, and 60s are the sandwich generation; looking after their elderly parents and teenage children, so the last thing they need is to be a servant and slave to a neighbour as well.
Help in an emergency - yes of course, and most people would - and should. But to become a regular help for a neighbour is a tie, an inconvenience, and a bloody nuisance. It's bad enough if it's a family member, as it can become a burden, but to do it for a neighbour, when, as I say, most people have a load to deal with in life anyway, is just too much of a burden.
I will help in a emergency, but will not help anyone on a regular basis, as I don't want to tie myself to the burden of being chief-cook-and-bottle-washer/servant/slave to anyone. I won't even take packages in for people now. Nor do I expect anyone to do it for me. Everyone has the opportunity to designate a 'safe space,' or have it delivered to argos, or morrisons or somewhere.
Not being funny, or mean or anything, but we have been burnt in the past, and have had people using us, and taking advantage, (on quite a few occasions,) and we have NO intention of going down that road again.
Good luck JurassicSal but I can't see anything changing unless you move. You are human, like us all, and sound very kind, and I believe you will find it very hard to say no to this lady.
And the fact she has got family is just an extra kick in the teeth! 