She was fully human, yes, and there is no sin in marital sex. If you were paying attention to what people were telling you all along, you would not have wasted all this bandwidth arguing these points, because no one disputes them.
It is even possible to read Matthew 1:25 the way you read it. In the cultural baggage of the 20th century that is even the natural reading. But it is not the correct reading in the context in which St. Matthew wrote his gospel. The correct reading is, St. Matthew did not know if Mary had marital relations with Joseph and was not venturing any guesses.
God isn't the author of confusion.
And the Scripture here is very clear.
Matthew 1:24 Then Joseph being raised from sleep did as the angel of the Lord had bidden him, and took unto him his wife:
25 And knew her not till she had brought forth her firstborn son: and he called his name JESUS.
It's not a bad thing for a married couple to have sex.