Ok, so this will be in the very very very very far future.

I’m currently studying to become an English teacher in a foreign country. Once I have my degree and TEFL certificate, etc, I plan on finding a teaching job in a foreign country, moving there, and staying for at least a while, if not the rest of my life. 

I have been to this country multiple times, and while the stays varied in lengths, I am ABSOLUTELY sure this is what I want. 
Although they were opposed to begin with, my parents are finally beginning to accept that this is what I want, and this is what I am going to do.

However, my mother recently told me that should they ever “need” me to, I “will come back to England to care for us from then on.” (I.e if they developed dementia, etc) She said it like I had no choice in the matter. Of course I disagreed with this - by that time, I plan to have a career and possibly a family in this foreign country, and she can’t expect me to just drop everything and become some stay at home nanny for her. At least, that’s what I think. 
She was appalled, accused me of not caring about her or my father, and stormed off. 

Of course, I would definitely come back to England to visit them whenever I could if they were ill - hell, I want to visit them and vice versa as much as I can every year regardless of their health. 

I just think that if they were to get ill, it is both unfair and irresponsible to expect me to drop my life in order to become their full time caregiver. I am not and will not be trained for that, and I wholeheartedly believe they would be better off in an old person’s home should they need to be in one. 

I love them both and care for them greatly so it sucks that my mother thinks I don’t. 

WIBTA if I stuck to this viewpoint? Is it rational?