that can be used as a temporary bonding agent. Sometimes it is a mixture of powder and liquid, but it usually looks like a small tube of superglue (don’t use superglue). If the temp crown is simply off, it could be used to tack it back in place. If there is a missing chunk, you mix it up with more powder to thicken it and it is basically a temporary filling. You’ll want to get in on Mon if possible either way.
I hate to alarm you unnecessarily, but if root canal treatment was successfully performed, I am surprised she is in pain. Perhaps it was only partially complete, but it sounds possible to me that there could be additional worries into the root area itself.