Hi Michelle
Destroy those cards and never think abt them again. Always tell yr daughter she is female, never forget that. You know she is 100% female from yr comments.
Re surgery, you have a lot of time to prepare. Perhaps a little abt sex ed around 7y.o. Tell her slowly and with kindness which I know you have. Slowly is all I can offer. Send her to an all female school if you can.
I was told abt the facts of life by Debbie in grade 5. She is now a ped neph... means she looks after the little ones with kidney problems. If you are from Melb, try to find her or Garry Warne, the only ppl I trust.
In the meantime, think and really think abt how you would recv this info if it were you.
Love