Do Catholics believe that Mary the Mother of Jesus is as holy as God?
The modified question is erroneous as it compares the holiness of a creature vs. Creator. The simple answer to the modified question is a definite No.
Below is the answer to the previous question which presented a more correct inquiry into the Catholic Church teachings in its over 2000 years history on why the Church teaches Mary was sinless.
Do Catholics believe that Mary the mother of Jesus as sinless as God is?
The simple answer is, God is a spirit and God is not subject to sin. While Mary as a creature having gifted with freewill and intellect can be subject to commit sin but by the grace of God was preserved & prevented to commit a sin. There are two kinds of sin were the Church believe & teaches that Mary was sinless. Mary did not commit any personal sin and She was also free from all stain of original sin.
Both Eastern Orthodox and Roman Catholic Church believe Mary is All-Holy and did not commit any personal sin during Her lifetime.
Panagia (Greek: Παναγία, fem. of panágios, pan- + hágios, the All-Holy, or the Most Holy; pronounced Greek pronunciation: [panaˈʝia]) in Medieval and Modern Greek, also transliterated Panaghia or Panajia, is one of the titles of Mary, mother of Jesus, used especially in Eastern Catholicism and Orthodox Christianity.
Most Greek churches dedicated to the Virgin Mary are called Panagia; the standard western Christian designation of "St. Mary" is rarely used in the Orthodox East, as Mary is considered the holiest of all human beings and therefore of higher status than the Saints.
Catechism of the Catholic Church also teaches that Mary is All-Holy;
493 The Fathers of the Eastern tradition call the Mother of God "the All-Holy" (Panagia), and celebrate her as "free from any stain of sin, as though fashioned by the Holy Spirit and formed as a new creature".138 By the grace of God Mary remained free of every personal sin her whole life long.
The Panagia or All-Holy pertains stated only that Mary was sinless in terms of personal sin but the Eastern Orthodox Churches is not clear in the full acceptance that Mary was sinless from the moment of Her existence stated in the 4th Dogma of the Catholic Church. The teaching on original sin is one of the factor as Eastern Othodox has a different view on this teaching.
*491 Through the centuries the Church has become ever more aware that Mary, "full of grace" through God,134 was redeemed from the moment of her conception. That is what the dogma of the Immaculate Conception confesses, as Pope Pius IX proclaimed in 185*4:
The most Blessed Virgin Mary was, from the first moment of her conception, by a singular grace and privilege of almighty God and by virtue of the merits of Jesus Christ, Savior of the human race, preserved immune from all stain of original sin.135
The Catholic Church goes even further by identifyng Mary as the chosen woman from eternity before the foundation of the world.
492 The "splendor of an entirely unique holiness" by which Mary is "enriched from the first instant of her conception" comes wholly from Christ: she is "redeemed, in a more exalted fashion, by reason of the merits of her Son".136 The Father blessed Mary more than any other created person "in Christ with every spiritual blessing in the heavenly places" and chose her "in Christ before the foundation of the world, to be holy and blameless before him in love".137
135 Pius IX, Ineffabilis Deus (1854): DS 2803.
136 LG 53, 56.
137 Cf. Eph 1:3-4.
St. John Paul II the Great teachings affirmed Genesis3:15 that the chosen woman is the Blesed Virgin Mary. This prophetic passage is the important verse that directly answer your question as this verse speaks of "perennial enmity", meaning Satan had not touch nor infect his malice on the Blessed Virgin Mary from the moment of her existence.
Genesis 3:15 Douay-Rheims 1899 American Edition
15 I will put enmities between thee and the woman, and thy seed and her seed: she shall crush thy head, and thou shalt lie in wait for her heel.
MARY’S ENMITY TOWARDS SATAN WAS ABSOLUTE
Pope John Paul II
Mary’s faithful co-operation in the saving work of her Son made it fitting that she should be completely free from sin and share fully in Christ’s grace
For full text see this link: Mary's Enmity Towards Satan Was Absolute