Simple and straightforward:
* The prettiness of the wildflowers in the meadow was breathtaking.
* The artist captured the prettiness of the sunset in her painting.
* He was captivated by the prettiness of her smile.
Adding nuance:
* Her prettiness was more than skin deep; it was a quality that shone from within.
* The prettiness of the old town square was a charming contrast to the modern buildings surrounding it.
* The prettiness of the song was only surpassed by the raw emotion in her voice.
Using synonyms:
* The beauty of the wildflowers in the meadow was breathtaking.
* The artist captured the loveliness of the sunset in her painting.
* He was captivated by the charm of her smile.
The best way to write "prettiness" in a sentence depends on what you want to emphasize.