You know the type — for every idea you suggest, she's got one better. She takes the cupcakes you baked for your kid's birthday and trumps them an elaborate, three-tiered cake for hers.
How to Handle Her: Be confident in the value of your own contributions and ideas. If she interrupts and attempts to one-up you during a meeting or conversation, say, "Can you hang on just one minute? I want to finish my thought." If her contribution to the class event is intentionally elaborate and showy, compliment it, then move on — no big fuss required.