I have a feeling that too many folks moved into the Peterson home and the girls left. HMR and JW seem to have broken up between late Aug/2014 and Nov/Dec 2014. Oddly enough, GW4 and his wife, filed for divorce in Nov 2014, and it was finalized 1/21/2015 (See Adams Cty Court Records). Whether that's when Mom & Dad moved into Peterson or not, Idk, but I still believe that something happened between the date in August when she was in love with her "best friend", and December, of 2014. Even if it was just that she got wheels, a license, and freedom.
Fwiw, HHG and FR, seem to have started seeing each other around Oct. 2014, and HHG's relationship status changed, to In A Relationship w/ FR, on Dec. 3, 2014. Her brother may have been hanging around a bit and become friends with FR, and he and HMR hit it off. Could have been just a rebound thing, after she and JW split. Four years is a long relationship.
If you'll note, both W boys were attracted to women who were polar opposites of their mother.