You see, at just the right time, when we were still powerless, Christ died for the ungodly. Very rarely will anyone die for a righteous person, though for a good person someone might possibly dare to die. But God demonstrates his own love for us in this: While we were still sinners, Christ died for us. Since we have now been justified by his blood, how much more shall we be saved from God’s wrath through him! For if, while we were God’s enemies, we were reconciled to him through the death of his Son, how much more, having been reconciled, shall we be saved through his life! Not only is this so, but we also boast in God through our Lord Jesus Christ, through whom we have now received reconciliation. (Romans 5:6-11)
Therefore, just as sin entered the world through one man, and death through sin, and in this way death came to all people, because all sinned— To be sure, sin was in the world before the law was given, but sin is not charged against anyone’s account where there is no law. Nevertheless, death reigned from the time of Adam to the time of Moses, even over those who did not sin by breaking a command, as did Adam, who is a pattern of the one to come. But the gift is not like the trespass. For if the many died by the trespass of the one man, how much more did God’s grace and the gift that came by the grace of the one man, Jesus Christ, overflow to the many! Nor can the gift of God be compared with the result of one man’s sin: The judgment followed one sin and brought condemnation, but the gift followed many trespasses and brought justification. For if, by the trespass of the one man, death reigned through that one man, how much more will those who receive God’s abundant provision of grace and of the gift of righteousness reign in life through the one man, Jesus Christ! Consequently, just as one trespass resulted in condemnation for all people, so also one righteous act resulted in justification and life for all people. For just as through the disobedience of the one man the many were made sinners, so also through the obedience of the one man the many will be made righteous.(Romans 5:12-19)
Now the sting of death is sin: and the power of sin is the law. (I Cor. 15:56) Your church doesn't claim that Mary escaped death. They only stated that her body didn't rot in the grave but was glorified and taken to heaven before anyone else would be. Because Mary DID die, she cannot be sinless because death is the consequence of sin. Jesus' death on the cross was because He took upon Himself the sins of all humanity - past, present and future - and not due to His OWN sin. The wages of sin is death, but the gift of God is eternal life through Jesus Christ our Lord. (Romans 6:23) What is firmly rooted in Scripture IS that ALL mankind are sinners and we can never be as righteous as God without the imputed righteousness of Christ given to us by the grace of God through faith. Mary's salvation from her own sin came through the same kind of faith in Jesus Christ as ALL will who receive the gift of everlasting life.
Your assumption: “Because Mary DID die, she cannot be sinless because death is the consequence of sin.”
You don’t know that the Blessed Mother died and your statement of the Blessed Mother’s sins is contrary to the determination of Jesus Christ’s Church and the inspiration of the Holy Spirit.
You seem to ignore God’s ability to do all things for Mary like the Immaculate Conception, Perpetual Virginity and the Assumption.
Mary, the Mother of God, was a humble servant that did God’s will and sacrified so much for her son Jesus. She is our role model to do God’s will.
Mary’s pivotal role in salvation history did not end with her giving birth to the Son of God, but rather continues to the present time.
If we were to take 1 Timothy 2:5 (above) in a sense that bars the participation of others in Christ’s mediation, then we would have to admit that we should not ask anybody to pray for us, nor should we pray for others.
But that is an unbiblical position! If we acknowledge that we can pray for each other as members of the Body of Christ (e.g., 1 Thessalonians 5:25; 2 Thessalonians 1:11), then surely we would want the prayers of the woman whom all generations call blessed (Lk. 1:48). After all, not even death can separate the members of God’s family (cf. Rom. 8:38-39).