Did anyone else's toddler change once they started PreSchool?

My daughter started preschool about a week and a half ago. She is 15 months. Ever since she started, she has gotten an attitude. She isn't as sweet as she used to be at all. She doesn't want to get dressed, she doesn't want to take a bath, she won't sit still for a book, she's been whining about everything! All of these things used to make her happy and we had fun doing them. Now she won't hardly let me out of her sight and she even wakes up in a bad mood. I'm starting to wonder if there is a correlation between preschool and this attitude. Maybe she is picking up bad habits? Did anyone else have experience with this change, or am I just headed a little early into the terrible twos!?