Grieving while still living

For issues specific to caring for someone with mental ill health.
My mom has struggled with depression and likely a number of other mental health problems her entire life. Recently, she has started more outwardly projecting the blame for everything onto me, the only daughter. My education wasnt good enough (according to her, I have a PhD in science) to move anywhere in the world, and I made the horrible mistake of not - years ago - moving to a country of her liking where we could build a new life. My mom sacrificed her life for me, staying in a country she hated. Now I am 'ungrateful' and 'disrespectful' because I have not given back to her sufficiently. I spend on average 2-20 hours a week working on issues for and with her. Trying to help her earn any amount of money to keep her going. My biggest offense recently has been living in the UK (not where I am from and not where she wants to live, so she "can't" be close to me), and now getting engaged to a brit. What should have been such a happy time has been completely devastated and I can't even set a date for our wedding because of it. At first she seemed happy and even toasted to the engagement.
Now, my fiancé is dirty, earns less than me, our house ir horrible... etc etc etc. I have been caring for her and protecting her my entire life. I am not anywhere near to stopping, but I need some strategies or coping skills for myself.

Anyone have any leads? I fit in an awkward space as I do work so I have earnings, and officially my mom only lives in the UK very part time. I do live here though so I guess my request is mostly to look after my wellbeing.
Accept nothing you will ever do will please your mum. I'd love a PhD in Science, if that doesn't please her, nothing will!!
Move away and have a happy life, or she will poison it. There are too many people here who have spent their lives trying to please parents.
Hi Chris
Your well being as a carer is paramount to us, and it sounds like, even if Mum lives mostly in another country she still plays the 'guilt card' that a lot of the elderly do.
Essentially you have 2 choices
1. You tell her if she doesn't stop moaning, you will break off contact, and do so. There's nothing less effective than an empty threat. This of course carries the danger that she then disinherits you and bad mouths you to all and sundry.
2. You put up with it all by setting clear limits as to what you will do, when you will do it and ignoring her the rest of the time, having made sure she has others provide the basic day to day care to keep her safe. I.e.. you become her care manager, but you are the one in charge and set the rules

The 3rd option is to carry on as you are...