I'd be worried, and probably do the 'are you ok?' text. Just because I like to know everyone's safe. Maybe agree with her to text when she's going to be away for more than 24 hours in future.
So here's a story for everyone who says "It's none of your business".
When I was in my twenties, I helped hire a chap from up north to come and work at our record shop (this is in the infancy of mobile phones). He wrote to his Mam every week to tell her all about London.
I worked different shift patterns as a duty manager, one night I went to the pub with a few friends as I was starting late the next day. We all said goodnight and he & I walked to the station together, we had tickets for a gig the next week, chatted, said goodnight & I went home on another line.
I woke up the next morning to find a million missed calls from work and loads of numbers I didn't recognise on my phone. I ignored them, assuming work wanted me to come in early to cover for someone.
It turns out our northern friend had fallen onto the train tracks and died.
The calls were from the police and work, desperately trying to find out if he was with me. There was nobody to officially ID him (me and a friend had to do it in the end) so the news could be broken to his family.
It haunts me now, every fucking day. If someone was living in my home, I would want to know they were safe, not where they were or who they were with. Just safe.