I hope she feels better soon
I had something similar with William when he was quite young. He'd been in the garden and came back in retching and pawing at his mouth. He sicked up some slightly bloody froth, so I was straight down to the vet with him. Turned out he'd eaten some Brunnera leaves and stems, which aren't poisonous, but are very coarse and had scratched his throat.
He was back to normal the next day so hopefully Penny will be too.