I never suggested she had an effect in parts of the game where she doesn't appear. You, the player, have to avoid the corruptive force. And when you don't, how is that corruption manifest? In becoming more promiscuous. The more that they share Ivy's world view, the more promiscuous the characters become.
Oh, you mean, like when she takes Holly to the gloryhole, and when a sufficiently big cock comes along, Ivy tells Holly to make room, so she can help. Yeah, that doesn't demonstrate that she's experienced.
Being promiscuous does not mean she doesn't have standards. It simply means when she finds someone who meets those standards, she'll respond in sexual, and physical ways, which she does.