Jesus Christ was 100% God and 100% man. To be man, He went through the normal gestation and birth process of mankind, God experiencing what it is to be a human from birth to death.
if I understand you correctly you were discussing that if she gave birth then technically she was no longer a virgin in your opinion, correct (note: I'm trying to understand what you wrote and personal interpretation is always faulty)?
That is not strictly true as virginity is rather dependent on the committing of the sexual act.
We all of course agree that she was virgin before and at the time of birth of her son Jesus Christ.
Now post that, just by reading scripture for direct references, you can only be ambiguous one way or the other if one ignores what others a the same time observed and believed.
We hold that she gestated the Lord for 9 months in a normal birth where like a normal mother and child the blood and nutrients were shared (hence the need for her own protection to be free from sin as in the presence of God in His purest form, sin cannot stand and we are stained with sin -- Mary was, for her own protection cleansed of the stain by God before her birth (just as we are cleansed of the stain of original sin by Christ's blood, so too was she, albeit in a different way)
Post the birth did she have sexual relations? the Bible is silent on this and Joseph disappears from the Gospel narrative post the Passover visit to the temple (mentioned in Luke alone).
I suspect some confuse virginity with chastity. Whereas chastity is associated with sex, virginity is more closely associated with a way of thinking.
1Co 7:34
(34) There is difference also between a wife and a virgin. The unmarried woman careth for the things of the Lord, that she may be holy both in body and in spirit: but she that is married careth for the things of the world, how she may please her husband.
Sex isn’t necessarily sinful, but it appears the colloquial perspective of the Virgin Mary remaining a virgin after the birth of Christ is obsessed with her remaining chaste in order to be considered without sin, which leads to even further rationalizations.