Does Daisy count as an Ivern unit and get a plus 1 might at a Brush Battlefield?

Yes, Daisy counts as an "Ivern" unit and will receive the +1 Might bonus from a Brush battlefield token.

According to the Brush battlefield token's ability (Rule 184.8), "Bird, Cat, Dog, Poro, and Ivern units here have +1 [M]." Since Daisy possesses the "Ivern" tag, she satisfies the condition for this bonus when she is at a location with a Brush battlefield token.