Need ideas for some fun with the other half. I'm looking for something similar to an egg in that it is in a fragile shell that can be broken given too much movement. Will be tying her up and filling her panties. But only want there to be a mess if she wriggles too much.
Sweet is preferred though savory is fine also. Have the potential for some diy if necessary as well
Going to be hard to find deliberately fragile containers, but in the spirit of eggs you could definitely get some of those plastic two-part Easter eggs and fill them with whatever you want. Depending on how well-made the containers are, the two halves will come apart with more or less jostling, but if you wanted to make them less reliable I would guess that sanding down the connective part a hair with, e.g., a Dremel would achieve the desired effect.
You could fill balloons with whatever. Use a funnel to fill them. Put them inside and tel her if she wiggles you will pop one at a time. Sometimes they pop on their own.