In the Vampire Diaries, S02, How come Katherine manages to get her hands on the exact same clothes as Elena and act as her? This happens multiple times throughout the season. Stefan asks this question to Katherine in one of the scenes but she doesn't replies.
That is because Katherine was a Doppelgänger who can take on the look and traits of Elena. Including her cloths and behavior.
It's an evil force that brings evil or misfortune.
It was mentioned in last episode of season 1, when Elena explicitly stated that her stuff is stolen. We even see Katherine straightening her hair to look like Elena. So Katherine did stole her stuff once, so can't she do it again? Even Jenna Sommers was in her control. And she was watching over them from long, so she should have learned to act like Elena during that time.
Below is the video fro Elena mentioning her stuff is stolen
Same scene get repeated in start of S02E01.