I think she's naive to think Richard wouldn't do anything to her, with what he's already done. What I don't really get is why she doing this to him, why she's so concerned in preventing him from finding someone he can love, like it affects her? It's not like she's ever been in love with him. They've certainly never showed any inkling of that.
I think it's because Gillian has becomed a self entittled witch. She's killed to get what she wants and lies as if there will never be consequences. She looks down on Richard with a cruel eye and words. She does cruel things, because she can.
I do hope Richard shoots her. I hope she sees it coming and that she lingers a bit before she takes the boat to hell.