but there's something about your phrasing which leaves me thinking that there's something weird about a woman who's attractive to you being insecure about her looks.

No. I've met enough people who fit that category that I don't find it weird at all. A little annoying and something to be discouraged if convenient but not particularly weird.

• The 'hot' evaluation is not a matter of who I find attractive but of who I evaluate as being considered attractive in general (or possibly what I think other people with think other people find attractive). She isn't exactly what I find attractive even though her general purpose hotness overflows into the wedrifid specific evaluation at least in part.
• I was referring to an indication of the verbal behaviour of people encountering Tina Fey (people saying that she is hot) rather than whether Tina Fey personally considers herself hot. Sure, personal insecurity can bias recollections about what people say and do but that certainly isn't covered in my phrasing - that's all in your reading!

Tina Fey lost a bunch of weight just before she got on TV. Given that there isn't really anything else to explain.

That would do it. She'd have been pretty and even attractive with the extra weight but 'hot' is rather more specific in this culture.