You know why it means that? Because Griffons normally eat horses, not mate with them, explaining why Hippogriffs are very rare. They are also obligate Carnivores, therefore they need meat and can only eat meat. But Gilda does not do it when she visits Rainbow Dash, instead eating stuff that she can not digest and will make her ill, risking to die a slow, painful death. But she still does it for her best friend.