Oh my.

What is she reacting to?

Her expressions are perfect - great to see what's going through her mind. The tags are also a nice touch and help to further build the story here. Kudos once again.

You guys must be new here. It's a colored remake of this of a gif the Admin made a while ago.

She's reacting to the lingerie she's wearing (hint: she likes what she sees).

I'm hardly new here, though it's been some time since I looked at the previous animation. I enjoy it when a piece gets revisited like this.

"It fits and..."

"Wow, I look kind of sexy...."

"I wonder if Master will get hard if he sees me...

"Oh god!...."

To be honest, the arms need a bit of animation, she looks stuck in that one position as she realizes she likes being showy

She's trepidatious and self-conscious, at first, at being so exposed and on display, but then she realizes how beautiful and sexy she looks and how the skimpy bra and panty set compliments her figure and its voluptuous proportions, and she falls in love with the ensemble and how they look on her, practicality gushing with giddy girlishness at how irresistibly temptatious she looks wearing them and can't wait to take them off for the right suitor -- or for that suitor to liberate them of her with unbridled lust as they ravage her femininity with abandon!!