The short answer is that legally, she wasn't the queen.

Henry VIII laid out a specific plan for the line of succession, should his son die without heirs: Mary, then Elizabeth, and then if they both died with no sons the throne was to pass to his younger sister Mary's children. His older sister Margaret's line was excluded from the succession altogether. His will said this, and he passed acts of legislation that were approved by Parliament.

Edward VI's will excluded Mary and Elizabeth from the throne, and also passed over the next claimant, Frances Brandon (Mary Tudor's eldest daughter), and named Jane Grey as his successor, but he died before his succession plans could be approved by an act of Parliament. He tried to bolster his decision with other paperwork, but none of it could override Henry VIII's succession plans without an act of Parliament to back it all up. Under the law, as it stood when Edward died, Henry's oldest daughter Mary was the legal successor to the crown, and Jane was essentially a usurper.

Jane does appear in some lists, with the "disputed" disclaimer. Historians have disagreed with each other on the legitimacy of her status - Eric Ives thought the naming of Jane as Edward's heir wasn't necessarily an illegal move (he wrote a book about her). Paulina Kewes has gone into the legal details to make the argument that Jane's elevation was invalid. (That link should provide you with an accessible version of her article, let me know if it doesn't and I'll try to find a different one.)

A comparable situation would be when Richard III took the throne after the death of his brother, Edward IV. Edward IV's son is included in the list of English monarchs as Edward V because he was king in the immediate aftermath of his father's death, as the eldest son of the previously reigning monarch - he wasn't disinherited until Parliament passed the Titulus Regius, which marked Edward IV's children as bastards and named Richard III as the king. Richard needed that act of Parliament to legitimate his reign. Jane never had it.