@Joanne63 I can totally relate. I raised three daughters, and get a lot of single female guests, of all ages, and I also get concerned if they don't return at a reasonable hour. Especially as it's a 20 minute walk to town and the beach from my place, and the vast majority of my guests don't drive here.
I had one female guest in her late 30's arrive, settle in, then go to town and didn't come back all night. I'm a night owl myself, so I went to bed around 1AM. But she had told me she had friends in town and was going for dinner and drinks with them, so I hoped she had just decided to spend the night at their place. I texted her in the morning to make sure she was okay- my suspicions had been correct and she apologized for causing concern. I also apologized for being a "mom"- said I couldn't help it, as the mother of 3 girls. She said she actually appreciated my mom brain. From then on, for the rest of her week-long stay, she would text me when heading home from town if it was after dark so I'd know if she didn't appear in 20 minutes, half-hour, that there might be something amiss.
Quite awhile ago, I started asking my guests for emergency contact info. It had occurred to me that if a guest had a serious accident, or simply disappeared, that their family would want to be informed ASAP. Airbnb does have a place for guests to enter this info on their account, but most guests have told me they didn't bother with it. And even if they had, I would think their family would want to be informed ASAP, rather than me having to contact Airbnb, then them getting in touch with the contact, maybe and who knows how long that would take. Also, if a guest sort of disappeared, and I had a family or friend contact, they might say "Oh, she does this kind of thing all the time, don't worry about her, she'll reappear at some point."
So, I'm really upfront with guests that I will worry if they don't reappear at some reasonable hour or text me to say all's okay, or let me know that their plan is to stay out late, letting them know that I can't help but be concerned. I've never had any guest balk at that, they all say they really appreciate it, and many of the single female guests do text when they are starting the 20 minute walk so I have a heads-up to be concerned if they don't show up.