[T]he notion of Assumption isn’t anywhere regarded as heretical. In any case, Mary’s resurrection only precedes the general resurrection to glory that all Christians will face. In the Anglican tradition, the doctrine is regarded as adiaphora (‘a thing indifferent’), but the day is regarded as a festival in the Church of England.
Contested by some, beloved by others, the Assumption remains a major date in the Church calendar.
That makes perfect sense (sounds exactly like something God would do) and is not in any way contrary to anything in the Bible.
Bible on Mary’s Assumption 
Biblical Arguments in Support of Mary’s Assumption [National Catholic Register, 8-15-18]
Mary’s Assumption: Patristic Analogy to Protestant Distinctives (vs. Jason Engwer) [8-15-20]
Scripture, Through an Angel, Reveals That Mary Was Sinless [National Catholic Register, 4-30-17]
Amazing Parallels Between Mary and the Ark of the Covenant [National Catholic Register, 2-13-18]
Biblical Support for Mary’s Immaculate Conception [National Catholic Register, 10-29-18]
Photo credit: Assumption of the Virgin (1650), by Guercino (1591-1666) [public domain / Wikimedia Commons]