[GreenHornet]

One would think her handlers would teach her how NOT to make those bizarre and inauthentic facial expressions.

I know that some people have attributed this to seizures, but I have a different theory. I think the key word in your statement is "inauthentic." Hillary is not a very warm person, and does not have much of a sense of humor. Consequently, when she attempts joke around or look like she's having fun, it's obvious that her facial expressions and body language are not genuine. As a result, it ends up looking bizarre instead.

[Blue Jays]

I agree with your assessment. Her issue could be both medical in nature and behavioral at the same time.
When she meets complete strangers for the first time she shows joy like she is encountering her favorite college roommate whom she has known for decades.
It is weird. Normal people easily detect that it is completely phony on her part.