Lying didn't seem like much of an option. She was already on to you. You decided to admit defeat and beg for forgiveness. "Natasha, I'm sorry, I just stopped by to say good morning, I swear, but then I saw your legs and I just froze. I couldn't move. I wasn't trying to stare at you, but you're just so beautiful! And then when you adjusted your legs and I saw your panties I ..."
"WHAT?" Natasha was shocked. "You saw my panties?" Holy fuck how did she not know that? She thought you were just looking at her legs? Oh boy, this wasn't going well. She just stared at you for what felt like forever. You were afraid to say anything.