Some people find out earlier. My doc told me the gender at 12 weeks and told me to not go and buy gender specific stuff until it could be confirmed at a later ultrasound. At my later ultrasounds (17w and 21w6d) it was confirmed twice. But there are a few ladies on here that were told one thing and then told something else at later dates.
Ur dr will probably tell u that u cant find out til 20 weeks because thats when they do an antanomy scan but u can tell u at 3d ultrasound place at 14 weeks & guarantee that their right for me so far its been right I had a ultrasound done at 16 weeks by my dr & they said its a boy :)
They're more accurate around 20 weeks. I'm not 100% but I believe their girly or boy parts form around 12 weeks, most techs don't like to tell you what gender is around then because the parts still look very similar to eachother
She might of had a 3d and some doctors will take that chance a guess that early. She probably will have a follow up appt to make sure that what they told her is correct.