but I have not yet heard of such evidence being brought before a court in an attempt to prosecute a provider for sex work.

In fact, I have not heard of any prosecutor using a provider's website as evidence at all, except perhaps in some unusual large cases like the Goddess Temple case out in Arizona.

Pretty much LE like to handle sex working cases in a cut and dry manner whereby they set up a sting, and catch the gal, or guy offering sex for money and then bust them for same.

So to her I would say, if she thinks having the hard core sex images/videos will help her business, go ahead and have them.  It should not materially affect her safety from prosecution.

Still not a lawyer

Shooting compensated porn in Maricopa County has already been declared illegal by the County Attorney.  So paying someone to shoot porn unless everyone is a volunteer would be a criminal enterprise.  The California case is non binding in Arizona and the Arizona courts could determine it differently.  

Fortunately, my friend is not located in Maricopa County.

explicit videos & even stills may attract LE attention.  But making a case based on photographic evidence, linking it to a particular person, their Ip amnd even computer & prove who used the computer...  if difficult to prove requires a lot of work.  Locate them & then arrest them...    

It's much easier to get the target in the room, get them to say the incriminating words & pounce.  

Now some jurisdictions have strict laws on operating a business, licenses for say massages, fire doors & exits, signage.  They can write code violations enough to drive a target out of business.  A member here reported this.        

In some cities such as Phoenix ads have been viewed as solicitation but would have to be more than naked pictures but something that implies a sex act for a fee arrangement (in AZ and many other states similar).   Long ago a Scottsdale escort was convicted of solicitation by a jury for ad that included "GFE".

Reviews can be more dangerous than ads.  While almost impossible to be introduced as evidenced at trial they have been used as probable cause for indictments or warrents.  Then LE raids and finds more evidence like phone calls, e-mails, texts that can be introduced as evidence in court.  

Further, in AZ all ads must include escort license number.  I have never seen one that complies as requires positive ID of all customers, where went etc and of course cannot include anything sexual.  In Scottsdale, it is criminal 15 days mandatory minimum jail on the first offense for not having a license and number on ads and carry ID card.  In Phoenix it is civil. It is civil in all of AZ but individual cites can make it criminal as some in the Phoenix area have.

It could prove criminal intent and state of mind of the defendant.  If she is offering sessions for a monetary fee then posts porn videos.