Im not sure what it is either, but she put that in the ad, so I figured somebody who's knowledgeable with arabians would know what it means. Also, what do you feel would be a fair price for a mare like her?
Honestly, up where you are, I have no idea. Down here, I probably would have a hard time giving her away. We're still suffering from drought and if you can sell at all it will be for peanuts, doesn't matter how good the horse is. Based on what I saw of her pedigree, she's really well bred, seller disclosed that she's SCID clear (but I'd want to see the results from the lab anyhow and an ethical seller would provide it no problem) but she's never been shown and she's not started so I wouldn't be looking to pay much for her. If you have thoughts of breeding her, I'd ask the seller if she's been tested for CA and LFS, both tests are fairly new and a lot of people haven't even heard of them yet. CA = Cerebellar Abiotrophy, looks like Wobbles but isn't and LFS = Lavender Foal Syndrome, mostly found in Egyptians but can be in any line and is lethal for the foal if 2 carriers both throw their LFS gene.
For price, pull up a sale site and narrow it down to prices for Arabian Mares in your area and try to compare like to like. For instance, 3 - 5 years, good pedigree, good looks, not broke, never shown. I'm going to guess it'll be under $1000. See if you can find 10 mares and check their prices and sort of average it out and see where you land.
To give you an idea of how bad it is down here, I have 3 weaners, all nice but 2 are definitely not Main Ring Halter material. 1 is pure the other half. 1 a colt, the other a filly. The 3rd one is pretty stellar and before I'll give her away, I'll keep her for a while. But the other 2, while very nice and would show well especially Sport Horse, if times were good should sell for around $1500 each. Today, with the drought, .........pfffft, I'll be very very lucky to get $500 for them, I'm thinking more like $400. The stud fee was $1500 for each mare, and vet costs........well, you see where I'm going. Needless to say, I won't be breeding much longer if this keeps up. In an area with plenty of hay, I might get $750 - $1000 for them, but I still wouldn't break even.
I hope some of this helps you. Good luck on your search!