[quote=Kaga]
I don't think you understand.It isn't a fake smile. It's a million miles away from a fake smile. It does not look like what a smile should look like. (Like, why does she feel the need to open her eyes super-wide?). And she also wasn't aware that the thing that she does when she's genuinely happy . It's like she legit does not understand the concept of smiling.
[/quote]

Maybe she just didn't think she smiled naturally? 
Understands what it looks like, but has no idea how to imitate one when asked.
Plus eyes do tend to get [i]somewhat[/i] bigger when one smiles, but not enough that I'd call it a notable feature.
Or something to explain away Henry's tendency to have super-wide eyes.

I don't know, like I said I may just not be grasping it right because I haven't seen this smile myself.

Does she recognize a smile when she see's it on someone else though?
Because honestly, this sounds more like a case where she just thinks that she specifically isn't capable, but understands what a smile is.
And because she thinks she isn't, she tries very hard to overcompensate for it.