Not sure if you're still researching, but I really like the Bluetooth ones.
For the Pi4, I use a little USB Bluetooth adapter from pluggable ($13-ish) on a 10-ft USB extension cable to get the module away from other things. I think the pi has Bluetooth built in? But I never got it working. But generic little Bluetooth USB things are perfect. With the USB extension cable I have great whole-house coverage (small house though)
Then for the sensors, I get a 3pk SwitchBot IP65 indoor/outdoor hygrometer.
They're on sale on Amazon right now for $25-ish for 3, so it's a pretty good deal.
As far as placement, I have some outside - they're fine. I try to place them where they're not getting totally hosed by rain or snow - under a tree or in the greenhouse or under my garage eaves sheltered from direct sunlight and rain.
They are very low power consumption (2x AAA batteries included) and I've had some running over a year and they still have more than 50% battery. (The battery level does report to home assistant)
They show up on home assistant immediately after powering up - no apps or anything needed. Just adopt them and set their location in the home assistant settings.
I mean ... Of your mom's still around... Maybe buy fish and like, ask to learn the recipe and cook it yourself? I'm not a mom, I'm a dad, but I cook a lot and if my kid wanted to learn what I do when cooking, that'd be cool.