They're not poisonous but they can cause bloat. Which can make them uncomfortable and it rights itself, or it can be very bad and kill them.
This is what you do if you think it's the latter.
Making sure she swallows, not inhales any of the below:
Syringe 40ml of vegetable oil followed by two teaspoons of bicarb of soda (baking powder) mixed with water.
The oil flattens the froth that happens in bloat, allows gas out of both ends! The bicarb helps get the rumen back to its proper pH.
Follow up with Pro-Rumen or since it's the weekend if you can't get it, live yoghurt watered down and syringed in.
Any significant change of diet can cause bloat, the rumen bugs react badly to having to digest different things.