"I'm not a prude. She is. She has no idea what she's doing, and you're going to make her fall madly in love with you. You're charming and great, and we know you're hot, and you treated me very well while we were working together. But Lydia... She's going to put your entire career in jeopardy."

Seriously, why would you trust her to keep such a big secret? No offense to Lydia, as Nancy did indeed adore her.