Canasta question

The deck is picked with sevens. The "picker" realizes there are only six sevens in the pack. She then proceeds to close her Queens. At that point she realizes there is a seventh seven in the pack, so she closes the sevens. She then has to discard, but realizes she is only left with "dead" cards. She has to take back the last thing she put down which are the sevens. You cannot throw a seven as the first discard. Does that mean she has to take back the Queen she used to close the canasta so that she can discard that? Does she also lose the sevens canasta?

I hope you can answer this question.