There are so many angles to start with this...let's start with TV. Kissing is displayed from time to time on the Disney channel. We don't overreact, but sometimes treat them like a commercial break. I am mixed about exposing her to it, as it does give them the idea, however, in another couple of years, they will be kissing each other, face it. And, they will do it even if we say it is not okay.
When you mention shame her, well, it is not necessary. It is natural, just not the right time. Our school (Parochial) has a not touching policy. So while my daughter loved to give hugs back in preschool, she had to learn not to touch when she got to school. There wasn't any shame in it, it was simply the policy.
It is likely the two snuck off to the room, not stopping to think that the others even noticed their disappearance, but they did. When "we moms" came upstairs and said no closed doors, that probably shamed them enough right there.
My daughter has played hockey with a boy since they were 5 or 6. They like each other and EVERYONE knows it. He is a sweetheart and doesn't let anyone hurt her, yet he will knock her down playfully. Last week, we gave up his time on the ice so she could try to get a hat trick. Any way, knowing that they do like each other, I like to keep my eye on them even though from a distance. The good thing is, it's too hard to kiss with those helmets and cages on!!! But, there are plenty of times to hang out at the rink when they aren't wearing them and the rink is where I see a lot of first crushes going on in the older kids.