But the Bible is clear that Jesus was the only perfect one.
Well, there's a difference between perfect and sinless.
But in any event, while one may joke about asterisks and all, if we are to take Paul with logical rigor, then Jesus sinned. But Jesus did not sin, therefore "all" does not mean "all". Therefore it is loosely said , and finding another instance of a sinless person does not take away from the point Paul as making when he quoted that psalm.
Further, the teaching is that Mary was not sinless by her own power but by a special grace. The common metaphor is that we have been pulled out of the bog by Jesus, while Mary was caught just as she was about to fall into it.
There is no "about to fall into it". We are all born sinners and we will all die sinners. Besides, I prefer my Mary to be human and not made into a God..I like her better that way, I can relate to her. Only those who have a need to see themselves as Gods need to create Gods of those they adore.