If she finds it, the insinuation would be that you have no privacy in your room. I sure hope I'm wrong.
If that is the case, the two of you need to talk and lay ground rules. Once my children hit puberty, they're entitled to privacy and I would never go through their personal drawers. They do their own laundry, make their own beds and clean their rooms. I have no reason to doubt them so I respect their privacy. I knock on the door and wait for a response before I'll even open their doors. They respect me, I respect them.
At 18, your mom should respect your privacy for sure.
I'm not sure why you're asking if that's not it. Unless you want her to buy it for you?
In that case, get a job.
