Well, if she is: good for her. Aren't most children born out of wedlock these days? I believe in the UK -where HSH lives- it surpassed the 50%. If she wants to have one she should have one, regardless of what her Opus Dei relatives or anybody else thinks.
I didn't know she was also working for Vogue, it seems rather popular under the daughters of rich aristocrats. Did the princess study art history IIRC? There must be more interesting &less stereo-typical things to do with such a degree.