I say the bitch died man...
THE BITCH DIED!!!lol
All joking aside. Queen Zeal just seems to me like she's a religious fanatic. I don't think Lavos has willingly corrupted her, since it has always been sleeping until someone very annoying wakes it up and it destroys everything. She simply found out about Lavos, found out its potential, but I don't believe she has ever communicated with the thing and made a deal with it. Her name matches with her personality. She sensed a powerful force, and thought to communicate with it and gain a portion of its power. Then she began to act overzealous and would go to extreme measures to see the thing with her own eyes, even at the cost of her own children and her kingdom. I mean, I do think she had the corruption within her the whole time. But being around Lavos causes corruption? I think not. Then our heroes would turn out to be the same as Queen Zeal.
This is how I see it;
Something bothers Lavos and it notices that it's coming from the surface of the planet.
It wakes up and wants to destroy everything.
It appears in front of people that were in the same room as the Mammon Machine.
Zeal jumps on top of it and starts to blabber some useless dialogue.
Lavos is like 'wtf mate? bah I won't bother with her. But the blue haired dude looks like the strongest of all of them.'
Lavos starts to drain Magus' energy.
Magus tries to beat him with a red... stick... (wtf SE? should've changed the graphics in the DS)
Lavos is like 'pfff what a panzy, and who is this woman on top of me again? oh wait look, this red haired punk is in front of me'
Lavos kills Crono.
Schala sends everyone out of harms way.
Lavos presumably notices Schala's power and starts to merge with her as soon as he is defeated by the party.
Lavos, in order to just not deal with Queen Zeal, it humors her and grants her the Black Omen.
Queen Zeal is chasing an impossible goal and thinking that worshiping Lavos will grant her immortality.
So like all religious fanatics, in the end, they all die for nothing.