@Selfishsally setting boundaries becomes weirdly addictive over time.
From experience I can attest that as a prior 'push over' and innate people pleaser, people have taken advantage of me many times over the years. That said, once you see the change in people's behaviour when you toughen up, it pays dividends a thousand times.
I set boundaries with my own family, my sister in particular and she doesn't rely on me anymore. It's bliss. In the past pitcher up to live with me after a break up where she lived rent free, added to my food shop but didn't feel the need to pay, came in on zero hours sleep and slobbed around my living areas on a Saturday, oh I don't know, when maybe we might want to use those.
I took a picture of her hungover sprawled out asleep in the middle of the day one Saturday on my sofa having left her lunch perched next to her like it was some kind of student digs, even when I asked her to go upstairs so we could enjoy Saturday evening in our own living room, she still refused to move, she parked herself there all day and had no shame. Oh and she was another one, shouted at me in my own home too.
I had done so much for her over the years, treated her like a daughter of my own ( she is significantly younger) and tried to make up for the fact our mother was never a mum to us.
Over the years she just knew she could push me around and I had enough. Kindness is often mistaken for weakness.
Im about to set boundaries at work with someone who reports into me and thinks they can do my job better than me and isn't shy to voice it, I've had enough of their disrespectful behaviour towards me. It's my own fault, I've been far too pally and nice to them and they are trying to take my job not even under my nose, just by being blatantly rude about it.
Although I've built the muscle memory but it takes a lot of practise to stop putting yourself last. Start today and say no and I guarantee you over the next year or so, she will start offering to help YOU.