The Palace Master looked no difference from a 20-year-old young woman, and her beauty made it difficult for one to take her eyes off of her. Coupled with her bright and inviting smile, she was most definitely a femme fatale.
One had to know that dao experts often went through cycles of appearing young and old. For example, Viola was currently aging and had the appearance of an attractive woman of about 40 or so years old. But, the moment she broke through and gained another 100 000 years of life, she would once again look like she was in her 20s. That said, this was difficult to do considering she was already a middle dao expert. It could very well be the end of the line for her.
However, geniuses of Jasmine's caliber never stayed in one cultivation stage long enough to age. In all likelihood, Jasmine would look this way until she was lucky enough to become a Higher Existence, something she had a high probability of doing considering the fact she was a False True God.