Be thankful that she is being open with you. Listen to her with interest. She doesn't know why she is feeling, she just knows she is feeling. Some things just excite kids that way. When I was young, around 10, I was attracted to tweety bird in the cartoons with Silvester. I look back now in disgust. Wondering how I could have felt like that towards a cartoon character. Things come and go. Just be there to see the path with her and to guide her. Heck, if I told my parents how I felt towards tweety bird, they couldn't explain it away. LOL
Ok, I am relieved that I'm not alone here. My daughter, also 6, just informed me (right after seeing two people kiss as well) that it makes her "pee pee tingle" and that it makes it feel like she has to go pee. I've always been completely resolved that I will never make my kid feel embarrassed for being open, that I will never treat her like something about her body or the way she feels physically or emotionally is "wrong"....but she's only SIX, so when she said this I couldn't help but kind of frown and look at her incredulously and then I just kept going about my business. I wish I would have reacted differently, that I would have known EXACTLY what to say without being dismissive or without making it taboo. I do remember in kindergarten that I was very curious, even kissed a kid at the bus-stop (most innocent kiss EVER) and I remember I would be aroused in a way. Still though, six seems a bit young to be aroused so strongly like that. Siggghhhh, wish they could just stay babies forever.
Could be medical issues there is case that puberty early set puberty
Is it normal for her to call her vagina a pee pee? Yes, I would say it is normal. But not calling her vagina a pee pee. Please use correct terminology for her parts.