“Also, calling someone a sinner without evidence is slander. Where’s Mary’s sin in the scripture?”
The apostle who took Mary in, John, would know something about who was sinless and was not. (1 John 1:7-10)
[6] If we say that we have fellowship with him, and walk in darkness, we lie, and do not the truth. [7] But if we walk in the light, as he also is in the light, we have fellowship one with another, and the blood of Jesus Christ his Son cleanseth us from all sin. [8] If we say that we have no sin, we deceive ourselves, and the truth is not in us. [9] If we confess our sins, he is faithful and just, to forgive us our sins, and to cleanse us from all iniquity. [10] If we say that we have not sinned, we make him a liar, and his word is not in us.
Yes, so those who "walk in the light", like Mary did all her life, do so because "the blood of Jesus Christ his Son cleanseth [them] from all sin". Mary was sinless because Christ saved her as well (Luke 1:47). Note that she never said that she was sinless, she simply was.