On young people leaving home

Dear Bros,

What is the Traditional Catholic teaching on young women leaving their household to live on their own.  My 20 year old was contemplating the idea and I having been raised Mexican Catholic was taught it was wrong and disgraceful for a woman to move out on her own.  So I conveyed that to her and I had her talk to a priest from the CMRI whom I expected to echo my wishes to her. Instead he "recommended" she not leave but assured her there was no sin in it. 

So I asked an Old Catholic priest I met and he said it was a sin because the 4th Commandment is broken and a women should be under the care of a man (her father, husband, or in a convent).  I myself believe it is a grievous sin to defy one's parents' wishes to simply live independently (that's how I was brought up). Who is correct here?

No hurry but please do respond. Thank you and God bless.

M. M.