My roommate never pays her rent without being reminded so I'm going to hide her things.
There's better ways to get her attention. Why would you do that to her?
I want her to pay rent on time.
I understand wanting to have rent paid on time. But taking her things without telling her is wrong and disrespectful.
WTF it's in my house it's okay for me to do what I want with her things.
If your roommate is paying her rent, even late, it is her house as well so you can't just go moving her stuff to make a point. I'm sure you are frustrated with her but you can do things like make reminders or simply talk to her about how mad her forgetfulness is making you, but if you just hide her things you will end up in a fight.