Imagine her sucking your dick with her delicate lips and flexible tongue.
Imagine her surprise when you cum too fast.
Imagine her getting mad but then tasting the cum and start gulping it down.
After she'd a taste of your cum she would slowly get lewder and lewder as she requests more cum.
The next time you have sex she will start to get mad if you don't cum in her mouth withing 45 seconds.
From now on the only thing she values is if you can cum fast, hard and repeatedly.
There's a reason why she kept covering her mouth, and why there's a number of random scenes where the bottom half of her face are cut off from the frame.
Guess we'll have to decide for ourselves. It's just that there's a lot of scenes where she places her pretty hands on or near her cute little mouth, and also lots of random scene like this where they didn't show her mouth at all.