You would do well to first note that Paul, in Romans 3:23, was generalizing a universal condition so as to make a point. Here it is in context:
…a righteousness of God has been revealed, being testified by the law and the prophets; even the righteousness of God through faith in Jesus Christ to all and on all those who believe. For there is no distinction, for all have sinned, and fall short of the glory of God, being justified freely by his grace through the redemption that is in Christ Jesus;
Do you see who Paul is speaking of? Paul was talking about people who do not believe when he said they “all have sinned”. In the next verse, he says that all are “being justified”. Does that mean that everyone is justified? No, but only “all those who believe”. It is the same with verse 23; Paul was not saying that all people everywhere are sinful (otherwise it would include Jesus), but only that everyone who disbelieves is sinful.
He then ties this together as being the reason that they need to convert. Paul is trying to stir up the Romans to convert the pagans among them, because Rome was at that time a very pagan city. It would be silly for him to talk about Christians being sinful; We don’t need to convert, because we are already Christian! No, he was saying that the unbelievers are sinful, and therefore they need a savior, and therefore they need to convert.
Conclusion? Neither in this verse nor anywhere in any way did Paul ever imply or intend to imply that Mary was sinful.
Mary did indeed say that God is her savior. If you take Mary’s claim that God is her “savior” to mean that He saved her from her sins, then you’ve got even bigger problems:
He was her “savior” before Christ was even born. Apparently, if this means salvation from sins, then Mary was saved in a special way before the grace of Christ entered temporality. In other words, it would be as another poster said: Mary was saved before she fell into the pit.
But I don’t think she was using the term “savior” in that way. “God my savior” was a very common Hebrew idiom (see Psalms 43:5, Psalms 106:21, Isaiah 43:3, Isaiah 45:15, Isaiah 45:21, Hosea 13:4), and antedated the Christian teaching that we must be saved from our sins. No one in those days had the concept of needing a “savior”, because your local priest could simply atone for your sins by sacrifices. “God my savior” in those Old Testament days simply meant God provided a way out of disaster, as He did to help the Israelites escape their captors by giving them passage through the Red Sea. God was the “savior” in that sense, and that is the sense which Mary used, and in no way did it mean that God had saved her from her sins, because that concept was not even around yet.
So, no, neither of these passages gives any indication that Mary was a sinner. She was saved in a completely different, more special way than any of us. She didn’t need saved from sins she committed, but rather she needed to be saved from falling into sin at all.