All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
It is not obligatory upon the person who misses a prayer or more to perform Ghusl, as missing prayer is not among the acts which make Ghusl obligatory. But it is due on him to make up for the missed prayer once he remembers it, and along with that, he has to repent to Allaah immediately in case he has left it intentionally.
Also, your friend should hold her tongue from giving Fatwa lest she says about Allaah what she knows not. For further information, see Fataawa 85264, 89978, 84645, 86918 and 84093, and this last one is about the things that make Ghusl obligatory.
Allaah Knows best.