The second means that the films are very saccharrin or sweet [treacly; treacle is a very sweet dessert tha some cannot handle over to the super-sweetness of it] but if one really looks into the films, they are not that sentimental or unrealistinc [this is usually a description of ‘Pollyanna’]

Probably not part of your assignment, but sentences were written badly.

The last part of the second sentence is an addendum and would flow much better if you called attention to that fact. It can be re-written many ways, but I would…

Hayley Mills’s films have been called treacly, although most of them are not so sentimental: they do not deserve that description.

I agree with what the first person said, the first sentence over uses vocabulary. Reminds me of an episode of Friends when Joey discovers a thesaurus.

I am a math teacher and I know that

2. Some people say that watching Hayley Mills’ films is like eating a dessert made out of pure sugar, but most of the films are not that sentimental.

In the second, the films are called sickeningly sweet even though they don’t really have very much sappy emotional emphasis.