Hmm. Alright, I guess it depends on whether part of Jvan is still a fraction of the splinter-mind or whether it's just the collective consciousness of Jvan's cult using Jvan's creations to communicate.

If it's the former, she's bound. "I wasn't completely myself" isn't a valid excuse. If it's the latter, Jvan's cult as a whole would be bound forever more unless the collective consciousness is completely erased and remade in a different form, but perhaps Jvan herself would not be bound throughout that case.

If I have to arbitrate Heartworm, I would rule that avatars of signatories are subject to the terms as well, seeing as they are technically still a manifestation of the deity's will. If Jvan did sign the oath, in order for Heartworm to be free from the terms of the contract, he would have to completely sever his connections with Jvan and become an independent entity, presumably a demigod or something to that effect.