Personally I think it's all a bit of a storm in a teacup, and one that will probably do the young lady's career no harm at all, but one should note that both Strauss and Hofmannthal both had in mind a slim, boyish figure to play Octavian; the reasons for casting the role as a soprano were both physical and vocal. I do think that, whereas one might accept a slightly larger Sophie or Marschallin, it is much harder to get away with a little extra weight in a role like Octavian, or Cherubino.
I have seen quite a few Octavians in my time, both on stage and on video - Sena Jurinac, Agnes Baltsa, Anne Howells, Brigitte Fassbaender, among others - all slim, all physically believable and, as such, able to help us suspend disbelief and imagine Octavian really is a boy, though, if I'm honest, Jurinac does have something of the pantomime principal boy about her, which can also be a trap of the role. Anne Howells was actually the most convincingly boyish.
Size can matter sometimes, and others not. For instance I have the DVD of Caballe as Norma from Orange, where her size and relative immobility bother me hardly at all, whereas in a telecast from Japan of the famous Zeffirelli Covent Garden Tosca, it bothered me rather more. The set had a rather high parapet from which Tosca would jump to her death. I saw quite a few sopranos in this production, most of them much slighter figure. The final plunge to her death was meant to be a mad dash to the finish, but Caballe started her slow ascent to the parapet for her suicide much, much earlier than any of the other singers. The guards would have had to have been very slow indeed not to catch her. This is when suspending one's disbelief can be a problem.