I don't think that's how she died, just seems like a moment Gosha is remembering that emphasizes how much they loved each other DESPITE their species... to put it into perspective, Toki was ready to suffer from komodo dragon venom to make their relationship work, while Melon's dad just ran away from his responsibility...
If she died from this kiss, then it's really gone to shit and gotten really fucking stupid, since they have had sex before.