Before the Thinner Disaster, Laralee offered Ortensia 250 E-Tickets in exchange for her locket so she could put it on display. However, the cat refused, since her true love Oswald gave it to her as a gift.
After the Disaster and the Projector Screen-powering machine broke, Laralee finds a Power Spark and puts it up for display. When Mickey asks for it, she's hesitant to part with it, but she'll be willing to trade it for something else. Talk to the Usher and get Hook's Cutlass from him. Laralee will happily make the trade.
Later still, if Mickey finds Ortensia's locket, the bad path is trading it to Laralee for those 250 E-Tickets. Although strangely, if Mickey does this, the locket never actually gets put on display.
Epic Mickey 2: The Power of Two
Laralee returns in Epic Mickey 2: The Power of Two, where she will will request that Mickey bring her some items to show in the Museum.