Amber and Paul were establishing a solid bond in episode one and discussing complex issues when he asked her if she would ever cheat on a partner. His question came right after Amber revealed that she was divorced after being in an unhealthy marriage.
In response to Paul's question, Amber referenced her failed marriage. "I'd like to think that I wouldn't, but I think it would've led down to that road, just because I wasn't happy."
Amber said that if someone cheats, there's usually an "underlying issue" though it wasn't "okay" to do to someone.
Instead of seeing her response as realistic and vulnerable, Paul told Amber it was a "red flag" for him. She then had to backtrack and explain that she hadn't cheated and would end another relationship before it got to that point. Awkward.