Hello there - I am currently studying the A Level Film Studies course, and co-incidently this question sort of came up in one of the early exercises...
The question was 'How have specific genres changes over time?' - and then the student had to chose from one of the principal genres, like 'Romantic Comedy'.
I had a quick crack at this, And although being a bloke, so not naturally the best student of RomComs I did feel that even I could see some changes to the attitudes regarding the role of women in these sort of movies...
Initially, I did float the idea that female characters, over time, have become much stronger and less stereotyped and that - I believed - that RomCom is the one genre where the normal male-centric casting lead is turned on it's head.
In RomComs - I guess because film makers believe that females are the main audience - the female is depicted as the stronger, more intelligent and witty lead. And it is the male that has become the stereotyped secondary character who is the brunt of the 'joke'.
HOWEVER, I remembered one of my favorite actresses - Katherine Hepburn - and how she brought a very strong and independent lead female to RomComs of the 40s.
She often had the best of her male counterpart and could be described as a very positive female role-model for the time and very much ahead of her time.
Though, to me, something went a bit awry in the 1950s and early 60s and female RomCom leads seemed to return to the shallow characterizations that we saw in movies made in the 1930s (IMHO - this ISN'T a research statement).
And even as the 1960s progressed we see actresses - like Jane Fonda who we now see as a political activist and feminist - as being involved in stereotypical RomCom roles like 'Bearfoot in the Park'.
How this bears on the films that you mention is contentious - ARE female leads these days positive role-models for young women, or are they simply regurgitating negative stereotypes?
Well - I'm a male so I find it very hard to guage these matters - Bridget Jones does *appear* to be a strong role model (almost in the Katherine Hepburn mould), but I have to ask why should her story have to be restricted to a Romantic Comedy?
IS this where the real sexism exists - that a strong female lead can only really be taken seriously in a light hearted genre?
For example, could we conceive of the film 'The Pursuit of Happiness' having a female lead?
(There is an aberration here, where strong female roles seem permissible in Action movies - 'Alien' and 'Terminator 2'.)
But otherwise, female leads seem to be generally pigeon-holed in the genres of 'Costume Drama' and 'Romantic Comedy'.
Hope there is something here that helps you - good luck with the project.