The NPC is called just Mabel. She is in Flipperton on Dolphin Isle.
To find the Golden Sheep in Horseisle, check out the link below.
Anywhere in forests you can find them. They usually are not on horseisle itself, but if you travel you can find them. You can also find them on horseisle if you look hard. Sometimes people drop them on the ground. Then you can just pick them up.
This is a very common predicament. First, make sure you've talked to the owner of the necklace. If she says something regarding Nolan... go talk to him again. If that doesn't work, follow the clue he would've given you before (if you don't have it, you should start using a quest guide... at least for long quests such as this one). If you have completed "Opal Sandstone's Sapphire: Ms Mabel Investigates" you may need to talk to Ms. Mabel. She will give you a Ruby, and a nice, hot cup of Tea, then try talking to Nolan again.
You can find Thoroughbreds on grass.
Please don't categorize this in the topic "Horseisle" as it isn't horseisle.
In the desert, on the ground.
You have to find the construction pattern for it and make it
hoof isle :)
Its in the GeneralStore on GlacierTon
You can find videos that walk you through horse isle deck swabs on you-tube or you can google "horseisle deck swab help".
You can find him living in a hut on the second Sand Isle.
You find them in appleton on horseisle. They are in the center near the apple trees and the pond. I believe they are on the flowers, which are the yellow and white dots that you see. Use your tools to find the seeds.