Sounds like she's your longest standing friend. But I don't think you can describe someone you don't see often as your best friend. I think best friend is your closest confidante.
I sympathise with you both though.
When you live that far from home town, your time on visits is so crammed and pressured with everyone you have to try to fit in that it can become really stressful to try to achieve the full set, and if you do manage it, you go home exhausted not having relaxed and enjoyed any of it.
To avoid this you have to prioritise the ones you absolutely can't miss out like parents and siblings.
So how realistically you get round it, you'd meet up on other occasions, specially to have quality time and see that person who got missed out of the 'I'm in town' session... but if you have a young family, and maybe money is tight, things like spa weekends are difficult, meanwhile something simpler doesn't make sense when it's a 7 hour round trip...
Long distance relationships are notoriously difficult for a reason.
It sounds to me like the heart is willing on her part, but the foundation of the relationship is mainly located in the past (sadly) and the difficulties are over taking the present day reality. Meaning that the impetus to move mountains to carve out the time isn't strong enough to win out often enough to keep things healthy and thriving in your relationship.
I think the fact that she did often make the effort to drop by and include you in what must have been a hectic schedule on her visits home show that she also values/d you highly and wanted to make it work, but sounds like the challenge of upkeep is just a bit too steep.
In your shoes, I would think of her as someone I think a lot of, who I would make time to see if possible (are you ever in her corner of the world) and would always feel affection for, but I would dial down the expectations of tending to the relationship regularly as the distance and other priorities are just meaning the expectations and the reality don't match in a disappointing way, through no one's fault.