My red got to this before I could get to her. If that makes sense she only took three or four nibbles. Is it going to harm her? It just came up in the redfoots outside enclosure.
Sorry, I don't know anything about mushrooms.
Some mushrooms are deadly toxic and some are harmless and edible. They can be very difficult to tell apart. At this point all you can do is remove it, check for new ones daily, and keep an eye on your tortoise. Daily soaks might help pass any toxins through.