It concerns Daisy’s name. Daisy is short for Margaret. I mean, it is one of the many, many short names that have been traditionally used for Margaret. People seem to be struggling with this concept, and I swear it’s true. It’s a fairly old-fashioned usage, and one that I’ve picked up from reading old-fashioned school stories (cf Daisy Pulls It Off), but it’s a perfectly valid short name, and one that I happen to prefer to Madge, Margot, Maggie, Midge, Meg, Megan, Peggy, Greta and Pearl, all of which are equally valid options.
So lay off – it’s her name.