Laughing while tantruming

Elise has started to do this really funny thing where she gets really worked about something and wants to tantrum, but when she starts, she finds the behavior really funny and starts laughing.  So for example, she will be crying in bed because I won't read whatever book she wants me to read (to stall sleep) and then she'll start thrashing her body and immediately start cracking up and then realizes she's still upset, thrash, and laugh again.  It is so hilarious.