What are you trying to get from this? Is this one of those uno reverse things?
It obviously sounds absolutely fine. 3 hour flight doesn't equal 3 hours door to door, what's the timings for the full travel?
I hope that my children feel they can live wherever they want and where they feel happiest. My boys both want to do careers that mean they can work internationally. My parents lived abroad when I was born, their parents were supportive of them travelling and following their career dreams and living in stunning places and the bonus of having somewhere special to visit on holiday. My aunts and uncles and cousins live all over the place, nationally and internationally. It's no reflection of the amount anyone loves or is loved and it's much easier to stay in touch now than it was in the 70s and 80s when my parents didn't live in the UK.
I want my children to be independent and live big lives but to still always feel welcome and at home when they're with us. I didn't create them to trap them.
I have friends who live abroad who come back for a month in the summer. They make the most of seeing family and friends then and it's lovely for them that they can earn so much where they live that they can do that.
That said, I live super close to my parents and one sibling. Reason being I have a step child we haven't moved further away as it's more important to us to have a close relationship with her. But the by-product has been being geographically close to family. I love that my children see their grandparents weekly or more. I love that they are close to their cousins and see them more regularly than we saw ours growing up. Being around the full year means we all get to do and experience the boring and regular things, not just the "let's have a BBQ because Ieuan and Michelle are back".
I've looked through some of the other comments now and see that you are the daughter who lives away. Sounds like you and your children have a lovely life. Is your mum maybe jealous? Is she hurt and sad because she'd always imagined you being nearby and being more involved in her grandchildren's daily/weekly lives? Do you have other siblings or are these her only grandchildren? I think that can make a difference. My parents get the best of both worlds with some grandkids down the road and some the other end of the country. My aunt loves being able to travel to amazing parts of the world to visit my cousins and their kids but she also absolutely adores that one cousin is still super close by and she's got an amazing relationship with their kids. Does your mum live in a grotty bit of the UK or in a fabulous place in the UK?
There's so much missing from the information you've given to get a proper understanding about where she might be coming from if she's giving the impression that she's anything other than proud of you.