A well reviewed, provider would have and should have her s*it together. If she has any sense she will brush her hair, be fresh and clean and looking like she would for a date! Unless the man "asks" me to wear jeans, or shorts or look like I just stepped out of the shower or bed then I look good.

You should NOT have to tell the provider to fix herself, that is JUST absurd!
If this has happened to you more then once then maybe you are choosing poorly? Read the reviews and see what the guys say about her dress and appearance. Or if you are really paranoid about this happening again then I suppose it doesn't hurt to email her before and say please dress up for me, or mention a certain photo you like of hers? Hopefully she will get the hint lol. BUt really if you are seeing well reviewed and well respected ladies this shouldn't be an issue.