Well goodness, that is a sight for sore eyes! The only ones of mine that have ever been willing to share are Mary and Flower, and they're just odd. Even if you give them two bowls, they'll share the first and then collectively move onto the second. Tudor also has one friend, Nomad, who's allowed a single mouthful of his dinner when they're in the same field, but never any more than that!
my three minis always share and will also share with my sect d gelding but my old mare won't tolerate any horse with 20 feet of her food or hay. I would defintely be calling a vet if she started sharing.