Dog eating my underwear.. Help??

Alright ladies.. I'm getting really frustrated and didn't know where else to post this.

So for the last year or so, whenever I would go home to visit my parents, if I ever left my underwear on the floor of my room my dog would eat it. Anything from a few teeth holes to full out ripping out the entire crotch.

Now that I have moved back in with my parents for summer, I hae been more aware to pick up my things, close my closet and room doors. But she has taken to rummaging through my dirty clothes hamper any chance she has. And the worst part is, she always eats my favourite pairs!! My oldest, ugly panties can be right on top of the pile and I swear she will dig through the bin to find the new, pretty lacy ones.

Just today, while I was at work she destroyed 4 pairs. Four!! I'm a working student and can't afford to sustain her panty-diet! And she never goes near my sister's (10) or my mom's (50+).

Anyways I guess my question is.. is this normal? Why does she do this? And is there anything I can do to stop it?

TL;DR: My dog is eating my undies.. what it do?