I've been reading articles about that very first press conference that her parents gave, shortly after they reported her missing. I find that I often see things that I didn't notice the first time around, and often the early articles contain things that people involved subsequently stop talking about.
Mother of missing Gabby Petito says boyfriend and his family IGNORED her desperate texts | Daily Mail Online
In this article, her mother talks about how his mother welcomed her warmly into the household, knit Gabby gifts for Christmas, and was very excited when the two got engaged. She goes on to say that she is now wondering if her daughter's relationship with BL "isn't what it seemed."
So, the idea that her mother had concerns about BL or didn't like her parents, doesn't seem to be true. Her father has said in interviews that he didn't like any of her boyfriends, but I don't get the sense that he had grave reservations about the relationship until GP went missing.
Given what we know about the stop in Moab, I think this means that GP didn't always confide everything in her parents, and may have put a happy face on things, even when there were problems. I have been in the position of not wanting to "badmouth" a boyfriend for fear that it would turn my parents permanently against him. I don't think it's uncommon not to share everything with your parents at that age.
MOO