... to do incall at a local hotel when a provider sets up for 2-3 days straight at that hotel?  Is it realistic to think that she can avoid security and staff with the in/out of hobbyists?

If she's only seeing one or two gentleman a day and is staying at a large upscale hotel with numerous entrances it shouldn't  be a problem   Now if she's seeing a lot of clients and needs a revolving door on her room, that's another story.  However, you'll probably never know how many gentlemen she's entertaining a day.  Many providers will change hotels  if they're in a city for an extended period of time. If you know the hotel already, do the room doors open to a hallway or to the outside?  Outside hotel room doors offer LE a better opportunity to monitor what's going on in a room. Is the lady well reviewed?

In my opinion, hotels often know when a provider is there...  as long as they are low profile & do not cause trouble.   2-3 days is about max IMHO.  
To reduce lobby traffic, I park nearer a wing exit.  Of course, I don't have a key card to enter (unless she lets me in as some do)...  so I enter through the lobby.  But when I exit, I take the stairs down & exit away from the lobby.  If I need to switch wings, I do so on an upper floor.   If nothing else it spoils someone watching the comings & going trying to time the persons leaving.
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I have worked computer support and like hotel staff I have found out suspected activities accidentally. I was not hired to police your actions so as long as you were reasonably discreet and not abusing it we would look the other way. If anyone complained like leaving your pictures on the color printer for anyone to see then we had to report everything. Basically  the lady is a paying customer and there is no profit in chasing paying customers away unless the activity is so obvious that it is going to cause complaints from other paying customers, or LE comes in looking for you.

that reflect on the safety and discretion of a provider. Not the most important and not a deal breaker.

Most reputable providers change hotels after one or two days. Longer than that, and they could begin to press their luck. I've also known a few who stay long-term in the same room. They may say they have an understanding of some kind with the staff. I don't put too much faith in that. Visiting them once or twice didn't strike me as dangerous. However, I wouldn't want to become a familiar face in the lobby.

I prefer not to see a provider staying in a hotel or especially a motel.  I guess that's from watching too many episodes of Cops.  Though typically, from what I've seen, they hole up in motels with their decoy provider who normally poses as a streetwalker.  We are not meeting streetwalkers and those shows aren't filmed in the safest parts of a city.

If you're going to see a known, well reviewed provider who is staying in a hotel then,  you have nothing to worry about as long as you're smart and do not draw attention to yourself.  Despite having some reservations, I have seen a handful of providers at hotels or inns without a problem.  As long as I can get up to the room without a problem, then it's cool.

The key is this: Act like you belong.  Good advice for many situations.