Moon asked for a spell that would help her kill an immortal at the cost of Eclipsa's freedom.
Eclipsa told Moon to aim for the heart and yet she aimed for the finger to make a point.
Whether or Not Toffee dies is not the contract agreement. Eclipsa claimed a contract between 2 queens is stronger than any magic but apparently takes a while to break through retard crystals unless Rhomboulous puts a new coat on her prison. When Toffee drained the old magic from the universe, the crystal doesnt run on its old stuff, thus Eclipsa can now break out easily. Star either needs to replace the magic or give her a new prison.