Grizel is described as "competitive" by Sandor, and she likes to make a game out of everything. She is also described as having feelings for Sandor, and Sandor confirms this by saying "she has gone to lengths to make that abundantly clear." Apparently, she joined the Elvin Regiments (goblins that serve the elves) just because Sandor joined it, and was even offered a position with the Goblin Queen's royal guard, but refused.
Aside from her the regular goblin appearance, she is also described to extremely lean compared to Sandor, but her "stealth and grace" made up for it. She has a long, silky ponytail.