How to deal with an over emotional child?

I have started doing a lot of research online regarding Over Emotional Children.

More and more I am starting to feel that Ali really falls into this category but I'm having a lot of trouble finding a true definition.

My definition is that for her, every emotional reaction is huge, extreme. When she is happy, she is hugely happy. When she is frightened her reaction is extreme. When she is frustrated, her reaction is extreme. She concentrates on an activity to the exclusion of all things. When she is upset, she is hugely upset. All things are big with her. BIG. But I can't find anything that describes this in children.

I found a lot of information on Highly Sensitive Children, which doesn't quite fit. Some of it does, her desire for order, cleanliness, some compulsive behaviors that she has. But a lot of it, dealing with sensitivity toward others, not there at all. I actually feel I am going to have to work very hard to create an understanding of empathy in her.

Her main issue, from my perspective, is that she is so easily overwhelmed and her only response is tears. She freezes up, and cries, and that's it. She has no other ability to deal with or move past the 'issue'. And the 'issue' isn't always clear.

This weekend I went to a new local Farmer's Market and brought Ali with me. All in all it was a little disappointing, but there was a cute little toddler sized playground.

She was having a great time until some older children started playing on it too. These boys were a little big for this sized play structure, but the real issue was that they were sitting inside the slides, so no one else could go down. I asked them to move once and they did, nicely, with no problems. I don't know if their parents were around or not, no one was upset by my asking, but no one corrected the continued behavior either.

After attempting to go down both available slides, and finding them both 'occupied', Ali just froze up and started crying. I calmly brought her down and we moved on.

I don't know if that was the correct way to handle it though.

She's two. Not Six. She doesn't have the ability to communicate herself well in situations whereas an older child can be expected to say 'excuse me, I'd like to go down the slide'.

But I don't feel like her reaction is altogether normal either and I am just at a loss.

I don't know how to help her. I don't know how much to help her. I don't know how much to push her to figure it out herself.