[Grammar] Having watched

[Maybo]

Having watched her as the wholesome country gal Hanna Montana ( a welcome 20- minute pit stop in the daily head-bashing sessions my twins used to entertain themselves with), it's quite something to see how she's transformed into thoroughly modern woman who's talented, funny, unafraid to say what she thinks and has an uncanny ability to stay one step ahead of the media and the zeitgeist.

What's the original phrase of " having watched", if I don't want to use participle?

Source: Marie Claire

 

[Raymott]

In this case, it's the author's opinion. So s/he means "I watched her as the wholesome country gal Hanna Montana. [As a contrast], it's quite something ... "
That's the basic meaning, but there's no reason to call this the "original phrase".