Not as likely as it might seem. It's quite easy to get hormones nowadays, whether legally through informed consent clinics (which pretty much just hand you hormones and a waiver), or illegally off the internet (probable here, since Narcissa's already smoking a bunch of weed and not leaving the house). SRS is different, since you pretty much have to see a professional for it, and that means getting a proper gender dysphoria diagnosis. A lot of trans cows try to fudge it for as long as possible, and then end up either rejected for SRS or not even bothering to apply at all.