You don't have to tell her that she's not the lady in the photo, not the same shape, not the same weight or hair or skin tone or that her photo does not represent her current age by a lot or her current weight by 50lbs.  She already knows all that - that's why her ad had phony photos.

 
You don't have to say anything if you don't want to.  She'll know exactly why you walked out.  Or you can simply say while turning to walk out: "Sorry, you're not even close to the photo in your ad.  Adios!

 
There's no need to be nice because she wasn't nice when she wasted your time with her phony photo.  But you do have to use judgment in every situation.  If she has a history of using phony photos, chances are other guys have gotten mad at her, so she may have some dude close for "protection."  If you think that's the case, then discretion is the better part of valor.  You may be rightfully upset but you should find a way to leave tactfully.

right here on TER.  

 
You'll find there is a bit of a divide. Some get really upset because they don't like "being misled" and for them that means near 100% accuracy. For others they generally don't expect photos to be accurate but do want something that is reasonably accurate or representative. Both side will agree that a photo that completely misleads to the point it was clearly intended to mislead is a bait and switch and none support such practice.

 
What to do? Well if you're not going to be happy with the session because the difference in appearances then you should walk. If not then you probably should not throw away you money and then complain about having done so as it was a choice you made but didn't.  

Alternatively, if you see someone behind the door that you find attractive, even if completely different, why wouldn't you stay? Worth calling out the situation in a review if you write them, particularly if the profile already exists and says something about them being accurate.

You'll also find many here place little faith in Eros Verified so perhaps you were lucky -- or perhaps just very good at reading the ads and the images so making much better choices that others.

Over the years this has happened to me a few times. Once I left. A couple times I was so horny I stayed and it works out ok, but other times I regretted it. You live and learn. My advice when meeting someone new is to be prepared for this eventuality.  Be ready to quickly exit by keeping your hand on the door knob and don't turn your back when you leave. You don't need to explain your reasons. If you are concerned about a handler nearby, you can say that you left your wallet in the car then immediately exit stage left. Amat Victoria Curam.

As far as I have been able to check (a couple of ladies have said the same) "Eros Verified" mainly means the lady or her handler paid a higher fee for the (?) badge and ad.

There are several ladies on Eros that I've seen multiple times and their ads are pretty truthful. But, I've also been misled a couple of times also. One was a much older gal, but the pictures were her; just about 20 years or so earlier. I stayed. She did provide a top notch service which matched her reviews.  The other ad was one that the gal at the hotel was a different everything. I walked.

Some good replies already, but I will add ...
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In a shared apartment setting or when Providers travel together and share a hotel room or have adjacent hotel rooms (e.g., the old Montreal GFs would often travel in pairs; the old Platinum Blondes would travel together), it is sometimes possible to say that there must be some mistake, "I made an appointment to see Mary, not whoever you are. Is Mary here?" ["I'm Mary."] "I meant the other Mary, the one in the ad photos." ["I'm Mary."] "I thought I'd be meeting the other Mary, in the photos. Thank you anyway. Bye."
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In an apartment setting, if they try to finagle the "Mary isn't here." or "Mary is busy now, but I can help you." you can counter with, "Thanks. I'll try another time when Mary (the one in the photos) is here. Bye!"
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It's harder to use that method with a solo indy, but maybe you can fake it ...  like she did.

This from the perspective of a frequenter of Asian Crapshoot Services, me. Every time I the door opens, it's a learning experience. One thing for sure: they *never* look like their photos or in any way meet the physical descriptions! For me, it has become part of the adventure. "Life is like a box of chocolates..." For the money, it works great for me.
   
But to your point, I have only been truly taken aback a few times, once recently where I was actually shocked (not in a good way). In the previous occasions, I have looked them straight in the eye and said nicely, but matter of factly, "no thanks," and walked out the door.  
   
This past time I actually decided to stay, but my initial physical reaction set things off in the wrong direction. She was not going to look past it so, after trying to get things going, I put my clothes back on, got my money back and left. I had to bite my tongue on the way out. Had I said anything it would not have been nice. (If curious, see link for my review of that experience.)

Fake pics? Fake pay.

or split your money between pockets

Inaccurate pics? Inaccurate donation.

I’ve never done either. But, if someone decides to try this, please report back here!

The expression on my face made her say......thus isn't gonna happen. Is it?