I really don't know if she fooled on him with this guy; but If they're together (or were seeing travelling together without Bryan) since December, she may have cheated on him; it's said Brysha broke up around October (yes, despite him being at her corner for her last fight)
Anyway, Bryan is 5 foot 9
but I get your point; and maybe Miesha's not the kind of person we all thought. I still have the feeling she may've slept with Cowboy when they had to travel to PA back in 2015 for promotions, and Bryan had to travel to London for the same reason at the same time...
Don't have any idea about Miesha's mother, but Doesn't she has a stepsister from the same mother and a different dad? And it's not like that sister is the youngest of all, it's her middle sister, so she may've cheated on him.