My Grandma Brought Up My Period?

Okay, so I've been having some really bad cramps with this period. And it's been heavier than usual and just overall, really really crappy. My Grandma is in town and was over at my house all day today while my dad was running errands and my mom was at work. We were kinda just hanging out and catching up. I spent a good chunk of the day just laying around on the couch and in my room. She'd just sit by me and we spent a lot of the day talking. After lunch, I was like "I'm going to go lay down for a while...my tummy hurts." She followed me into my room and a few minutes after I layed down, she put her hand on my tummy and was like "You're having a really rough period, aren't you sweetie?" I was shocked. I didn't tell her I had it. My mom didn't tell her I had it. Sure, I've been getting it for 4 years, but we've never talked about it once. How did she know that was what was going on? Do people REALLY pay that much attention to what's in the bathroom trashcan? I'm sure that if she cared enough to look, she would have seen my pad and tampon wrappers in there, but I guess I've just never really looked for that kinda stuff in someone else's trashcan. Was my behavior really that obvious? I just feel kinda weird about it now. Anyway, I was just like "Yeah...I'm having the worst cramps of my life right now. It hurts so bad!" She poured me a hot bath and made me some tea, and told me that she used to have a hard time with cramps the first couple days of her period, and that as she got older, hers were really heavy and she had to have surgery to fix it. This was a bonding experience I guess...but it's weird because we've never talked about that kinda thing before. Is it normal that I feel uncomfortable?