Not going to lie, when I read "Today, I visited my girlfriend in the preschool", I thought this story was going somewhere completely different.

It happens - she has now learned that you consume each and every media you present to children thoroughly in advance to avoid this. This is a good lesson if she will be working with children in the future. (And if she was aware of how the original version differed from the Disney Happy End, it's kind of on her for not instructing you or provide you with an alternative ending.) On the other hand, a lot of times children just pick up from your own displayed emotions. When I took my son to the screening of The Lion King, there was a mother with her daughter next to us. Now, Mufasa dying is a sad scene. But it takes like two minutes and is followed by the hyenas crashing into the thornbushes. So if you just say nothing and let the kids handle their own feeling for a couple seconds before the next comic relief scene distracts them again, everything is fine. But if you do it like this mum and lean over to hug your kid, sniffling "Oh it's fine the big lion is just sleeping I'm sure he's not dead" that kid cries, because mum is upset. So you might not even need to sugarcoat the ending of the little mermaid, just stay calm and matter-of-factly, the ending is very philosophical anyways and goes over most kids' heads. But if you or your gf act upset about it, the infectious crying starts. :/ Anyways it was probably a teaching moment for her as an intern working with kids in any direction, take it as such.