Two thoughts here.
One: some people are just not as self-aware of their own feelings/emotional responses to stimuli. In this situation, one person who has emotional OE's may well read another person's more muted responses to life as "flat" or "elusive" or even "dishonest/secretive" when it's just that those things don't make much of a ripple on the other person. In the extremes, of course, emotional experience can be pathology, but it doesn't sound as if that is the case here-- the OP is describing a child that seems to enjoy life in the moment, but not be that introspective (or communicative, anyway) about that enjoyment.
Two: some people (introverts, most notably) regard their feelings as intensely private. In this case, talking to other people about their feelings feels... well, intrusive is probably the kindest term. It's very distressing, and it makes the person experiencing it wary and defensive.
Just a couple of thoughts about this kind of thing. I tend to experience emotional highs/lows via emotional OE, and I have a spouse who does not. He is an extravert, but he is NOT a 'talking about my feelings' person. At all.
A third thought occurs to me-- is it possible that your child lacks some of the language to discuss emotions well with you? Some kids need to be coached to find words for their emotional reactions to life, and only then can they talk in more emotionally descriptive terms. Are those terms mostly absent in discussions in your home? She may really not know what it is that you are asking her when you become frustrated that she doesn't share her emotional responses to her day.
Can/does she talk about OTHER people's emotions? Using a proxy might be a way to bring up the subject in a less direct/threatening manner.
"Wow, Mr. Neighbor seems grumpy/quiet/withdrawn/sad today. Do you think he has had a difficult week? What do you think might have happened?"
