Unfortunately, the question is a bit flawed in its execution. England and its predecessor states (the Anglo-Saxon Heptarchy) did not allow Queens Regnant. (Æthelflæd, Lady of the Mercians, daughter of Alfred the Great, co-ruled with her husband and continued as sole ruler after his death, but had no hereditary claim to Mercia, which was by that point subjugated to Wessex. Her daughter, Ælfwynn, inherited in June of 918 after her mother's death and was "deprived of all control in Mercia, and was led into Wessex three weeks before Christmas" (per the Anglo-Saxon Chronicle).)

The only possible female holder of monarchy powers prior to the Tudors was Matilda, daughter of Henry I and the widowed Empress of the Holy Roman Empire (remarried by the time of her father's death to Geoffrey, Count of Anjou). Matilda was always referred to as "Lady of the English" not "Regina" or "Rex", and her ascension was famously contested and she never was indisputably in control in England.

(As a side note, it was not unknown for countries to use the title they used for "King" for both male and female rulers. For example, Jadwiga of Poland was crowned as "King" of Poland, and (to go much much MUCH farther back in history) Hatshepsut ruled as Pharaoh (complete with the pharaonic beard). It emphasized that the title "king" was considered to mean "monarchical ruler" and was not considered to be masculine-gendered because, logically, only a male could be the supreme ruler.)

The situation on Edward VI's of England's death was extraordinary. There were no descendants of Henry VII and Elizabeth of York eligible for the throne (according to Henry VIII's will) other than women. In 1553, the people eligible for the throne as per Henry VIII's will were:

The Lady Mary (later Queen Mary I)

The Lady Elizabeth (later Queen Elizabeth I)

Frances Grey, Duchess of Suffolk

Lady Jane Grey

Lady Katherine Grey

Lady Mary Grey

Lady Margaret Clifford

Henry VIII had excluded his older sister's line from the English throne (perhaps due to the logic that, as they were not natural-born English, they could not take the English throne). Even then, there only one known legitimate male-line option. Margaret Tudor's daughter, Margaret Douglas, had one son at the time of Edward's death, Henry Lennox. (Henry was born 1545-46, so would have been 7 or 8 at the time of Edward's death, which would have lead to another under-age king.)

Because of the way that Henry VII took the throne, and the number of possible non-Tudor contenders who had been executed between 1485 and 1553, it was very difficult to back up dynastically to lines prior to the Tudors (as was done in Scotland upon the death of the Maid of Norway) to determine other eligible claimants. Political and religious realities at the time, too, contributed to the disinclination to go that route; one of the major Yorkist claimants still alive, Edward Courtenay, was Catholic, so the cabal in control at the time of Edward VI's death would not have wanted to support his claim. While a Tudor dynast, Henry Lennox was also Catholic and thus the Protestant-led Council at the time of Edward's death would have had no benefit in attempting to overturn Henry VIII's will to bring him into consideration.

Since Jane Grey was never "legally" queen, the first queen regnant was Mary Tudor. From the beginning, English minds grappled with the disconnect in logic with having a female executive ruler. Was Mary a King, the title by which every executive ruler had gone by before, or was she a Queen, but with the powers of a King (the second choice was what was eventually settled upon). Mary herself, showing that she was not lacking the Tudor ability to do political spin, positioned herself as a "mother" to her people.

It was considered utterly impossible for a woman in such a position to remain unwed, and Mary agreed with that belief. Her marriage to Philip of Spain brought the only King Consort to date (and very likely ever) to England, and created a whole new set of problems. If a "King" was a supreme ruler in a country, then a "King Consort" was a contradiction in terms. Philip was viewed by many, both within England and internationally, as AT LEAST a co-ruler with Mary, if only because a husband had total legal control over his wife and it was antithetical for a wife to exert legal authority over her husband.

Mary's reign was from July 1553 to November 1558. When Elizabeth took the throne, she was able to step into many of the roles that Mary had pioneered, the most important being "a queen regnant is the same in power as a king regnant".

Elizabeth's longevity and ability to avoid marriage and thus avoid the tricky question of how to balance a wife's subjugation with a monarch's total authority cemented the English acceptance of a queen regnant. It very likely also helps that between the end of Elizabeth's reign and the beginning of Anne's (as the next queen regnant to rule alone), the English (and then the British) monarchy was substantially reduced in power after the Commonwealth and the Glorious Revolution.

(When Victoria took the throne in 1837, she had a living uncle, Ernest Augustus. It is my personal theory, however, that at that point Parliament preferred a Queen Regnant as a way of further weakening monarchal power. So while the argument could have been made that by strict male-preference primogeniture the throne should have gone to Ernest and then Ernest's son George, by that point a female monarch served Parliament's agenda better.)

You've received a good answer, OP, but I wanted to also share some past ones I've written on the subject (it comes up frequently):

Mary Tudor was the first queen regent of England. Was this noted at the time? Was there any significant reaction, positive or negative, to having a solo female ruler?

How were Female rulers Like Catherine the Great and Queen Victoria seen as capable of ruling when women in those days were thought of as lesser than men.

Did ruling Queens in historical Europe face gender discrimination?