10 year old home alone?

[Alwaysblindsided]

My friend has just casually informed me she is planing to leave her 10 and a half year old (year 5) home alone for two days this half term….
Am I being unreasonable to be concerned about this? She is sensible but still, only 10. She does have a phone and her mum works quite locally.
I tried to hide my shock, I offered to have her at mine on the day I’m off this week even though my children are much younger and they don’t know each other very well. She said she’d let me know.
I’m really concerned but should I be??

My own Yr 6 10 year old doesn't like being left home alone. But she's ok if her Yr 8 sister is here too. But I've only left them both home alone c. 3 hrs. All day seems too long for me.