My narcissistic aunt with Alzheimer's doesn’t recognize me in person and is very suspicious of me. Should I stop visiting her?

If the visit causes anxiety for her and you too, I would stop the visits for a while. Maybe as her Dementia progresses she will just consider you a visitor. Don't tell her your name. Seems to trigger something.

The Dementia brain is so unpredictable and I don't do well with that. My Mom said a few things to me too and I was the only one of 4 kids that did for her. Its the desease, the brain is dying.

Yes, you should stop visiting her. If she no longer even recognizes you, what's the point in seeing her in person?
Let me tell you something I've learned from many years of working in elder homecare. When you see your aunt in person and she is suspicious because she doesn't recognize you, that visit alone has unnecessarily complicated her life and the job of her caregivers. That upset will have regressed her and could set her back for days.
This is what happens with Alzheimer's/dementia. The slightest disruption in a routine can set them back for days.
Limit the amount of time you spend on the phone with her too. She's clearly out of it and can no longer hold a coherent conversation. Limit how much time you will spend on the phone with her. Answer one call a week from her.

How often do you visit? It sounds like you no longer want to visit your aunt but you're not sure if you should. It's like you feel a responsibility or obligation to visit so you're looking for advice. Well, you're under no obligation to visit. Neither one of you enjoy the visits. If you feel the freedom to be yourself in not visiting, then don't. If you want to visit a lot less often, do that, but don't feel harnessed to her every whim. Her life has been predetermined by her illness, yours is determined by you.

Yes, stop seeing your aunt if doing so will cause her grief. With Alzheimer's, you're not going to be able to convince her you're 'you' or anything else for that matter, so stop trying. Stick to the telephone calls since she seems to know you when you call her. She has no short term memory, so she insists nobody goes to see her in the NH when they really do. My mother does the same thing (with moderately advanced dementia); she continuously tells me that 'not a soul' calls her or goes to see her, which is 100% false, but there's no convincing her otherwise. It's just another sad part of an ugly disease where everybody loses.

If you want to go visit her once a month just to check on her and make sure she's okay, give that a try to see how it goes. You can always go check on her w/o her knowledge as well. You can visit from afar, while she's eating or doing something in the activity room w/o her knowing you're there. Everyone in a SNF needs an advocate to make sure they're being cared for properly by the staff.

Good luck