A woman can tell how much experience you have had with other women from the way you behave around her, from the things you say and do, and from the things you don’t say.
If you let her know that you find her beautiful, she will get the feeling that you have not been with many women, which means you don’t have much experience, which makes her lose some respect for you, and makes her wonder if she took the right decision by hiring you. She may pay your fees (because she does not want trouble) but there is a good chance she won’t hire you again.
Never show or tell a client that you find her hot or beautiful. Don’t give her compliments on her beauty, don’t be nervous and fidgety in front of her. Always appear calm, act as if her beauty is no big deal, as if you have been with much more beautiful women.
So should you never compliment a client? Of course you should, but not on her physical beauty like all the other loser guys do. Instead, compliment her perfume, or the mole on her back, or her choice of colours, or the way a strand of hair always falls on her forehead (if it does), or her sense of humor, or the shape of her boobs, the shape of her butt, the fragrance of her body, the aroma of her vulva…compliment anything except her “beauty”, only inexperienced guys do that and you don’t want to look inexperienced.