Her mom is a real piece of work.
It’s hard to stand idly by and watch someone get away with antisocial behavior. It’s not always easy to catch a thief or any other kind of petty criminal in the act. If your wallet is stolen, all you can do is cancel your credit cards and hope they don’t figure out your debit card PIN. Most police departments aren’t too concerned with catching the guy who stole your bike, because that’s a lot of hard work, and objectively less important than finding other kinds of criminals. They’d have to check security footage, track down the guy, and find the lost bicycle, and in the grand scheme of crimes, that’s usually not their priority unless you live in a sleepy town with the kind of dedicated police force you only see on TV. All cyclists can do is put more than one lock on their bikes and hope it doesn’t get snatched up.
We like to think of thieving as something strangers do randomly, but that’s not always true. A lot of the time, the people closest to us are the ones who steal from us, and it takes us a lot longer to notice because we trust them. I would not expect my friends to steal magnets from my fridge when I host a house party, and yet it has happened! It’s important to be vigilant with your belongings and your bank accounts. You can’t allow just anyone unfettered access to them. Sometimes, your own mother can’t even be trusted.