No offense, man, but it kinda seems like the girls in your life are trotting right over you. If it really bugs you, put your foot down, and tell her to get her own stuff (or buy stuff for her), that your wardrobe helps fit you, and that her wardrobe helps fit her. It might be cute a few times, but to wander off with more than what can be counted on one hand is a bit much. If it's the post-staying the night "I need something that I wasn't wearing yesterday" argument, then tell her to bring a change, or to keep a spare shirt and pants at your place, on the other side of your closet. Be firm, say your stuff is yours, and her stuff is hers, and that she wouldn't want you strutting about in her clothes, so the same applies.