Swollen tongue and mouth drooping


I just went out to tuck the girls in for the night and noticed my
cushings horse has a slightly swollen looking tongue and one side of
her mouth is droopy looking I think due to swelling, this morning it
looked swollen but the swelling went down and I thought maybe a bug
bite but it's swollen again, I still think it's a bug bite but
I'd run it past the group if anyone else had this experience. I
watched her a while and she's eating and drinking with no problem,
ran my hand in her mouth [as much as she'd let me] and can't feel
anything except it does feel bigger on one side. Hosed her face off
which she likes anyway and gave her some benadryl in case it is a bug
bite, maybe got stung by a hornet while eating grass?