Yes ! That is true. I know people who couldn't enter US  after being landed and I even know  one of my friends family members visa was cancelled by US embassy in kathmandu because of the same reason.  I advice you not to listen to anyone and bring her withen 6 months. Everybody has their opinion but In my case I have  been there, done that and  I was personally involved in 2 cases.

If you need further info you can email me.