I'd like to make a correction here. Jill is jealous. We saw it when our idiot said he was going to meet Zoey. But Jill, being shy and having good manners, didn't want to start a fight, instead she poured out her heart to Sage. Jealousy is there, Jill just didn't show it so openly.
And her absolute trust is more a flaw. She should check our guy more, she should watch Bianca.
Besides, forgiving everything is also a flaw, people will use her for it. I would never forgive stolen money, MC should be in a blacklist for this forever.