I' m confused about the Mistresses of the nursery to Edward IV's chi

Sorry to ask for help rather than contribute knowledge but I am struggling with some contradictory information about who was the Lady Mistress to the daughters of Edward IV and Elizabeth Wydeville.

I know EW was granted £400 a year in 1468 for the upkeep of Elizabeth of York and the next sister Mary.

I've read that the mistress/governess was Lady Berners. I know she had the post till she died in 1475. But did she start in 1467 or 1468? In a footnote in a Ricardian article The Royal Burials of the House of York at Windsor by Sutton and Visser Fuchs it says 1467. Normally I would trust their research above Arlene Okerlund, who implies that it was 1468 as she says Elizabeth got her lady mistress when she was two and obviously as Elizabeth was born in 1466 that's 1468. But the grant of 1468 makes me wonder if 1467 was a typo because would a mistress have been appointed before EW was given the grant for the daughters? Does anyone know?

Also I've seen Lady Berners named as Margaret and Margery. Is one right and the other wrong or is Margery a shorter version of Margaret? I think it can be.

And where does Elizabeth Darcy fit in? Laynesmith says she was appointed as Lady Mistress to the children of Elizabeth of York and Henry VII because she had been mistress in Elizabeth's childhood. I think Hicks in his Edward V says she was as well, but Sutton and Visser Fuchs only mention that she was the mistress for Edward V alone.

I would be very grateful for any help anyone could give. Thanks.