The amniotic fluid is there in the amniotic sac due to the new life bringing in the fluid from the connection between the uterus/womb and the placental implantation connection.
Again, the placenta is made by the growing child not the mother. The fluid in the amniotic sac is there by the actions of the growing child process. So, both the amniotic fluid (the 'water' with effluent content) and the bloody discharge would require the offerings. The implantation pregnancy in the uterus OPENS the womb.
The cervix is an os, a portal. Jesus was not brought into Mary's uterus via this portal and it is just as likely that He did not exit her body via this portal. The offerings indicate the water and the blood exited the portal (requiring the offerings), but to assume this means the BIRTH of Jesus came through that same portal is not a necessary conclusion. Just like it is not necessary that Jesus leave the rock tomb by the portal obstructed by the large stone.
But she was still a virgin in that she did not know a man, IOW, she had never had sex. Telling them they are not virgins even when they maintained their moral integrity and waited until marriage for sex is an insult to them.
The classic definition of virginity does a disservice to women who, for some reason or other, have their hymen ruptured although they never had sex. It's not their choice that that happened cause no woman is going to do it intentionally.
Mary didn't have sex with anyone but Joseph and therefore he still had the privilege of being the first and only.
Then there's the ridiculous stories I've heard coming from muslim countries of women who have surgery to make them "virgins" again for a second husband, which is ludicrous. They've had sex before and surgically altering that does not change THAT fact.
Again I say, “Why not?”