It also occurs to me: If she travels with her parents as you indicated, and then overstays to try marry and adjust, the implication is that her parents will clearly have lied at the port of entry about their reason for visit. She might get away with it, but they won’t. The next time they try visit her, the likely outcome is that the CBP officer will pull up this history, see they lied before, deny them entry and revoke their B visa. That is, if they she/they don’t get caught out the first time and denied entry anyway.
The short version: your attempts to circumvent the system may well result in 3 revoked B visas and no time together.
PS 40 is not a “girl”.