Traditionally, understudies aren't really rehearsed until after opening. With how much more careful everyone is with illness, they (the everyone "they", not this show specifically) really need to find a way to change that.
And to say "no rehearsal" isn't necessarily accurate. I believe she was rehearsed, but didn't have a put in. (Still, a big jump to performace level.)
If we're not having fun, then why are we doing it?
These are DISCUSSION boards, not mutual admiration boards. Discussion only occurs when we are willing to hear what others are thinking, regardless of whether it is alignment to our own thoughts.