I've not heard that the two were super close like that outside of football.
If it makes it pretty obviously true, then they did a poor job trying to hide it.
Is it not possible that she knows the Whitworths and attended with them. Obviously a random attractive chick hanging out with Whitworth's daughter means she's dating Goff.
Alternative theories: She's dating Whitworth's daughter.
She knows the daughter from... I don't know, anything (because people have lives) and attended the game with her as a friend.
She's dating anyone else on the team. She attended the game with her boyfriend who loves the Rams; they just happened to be sitting near the Whitworth family, the daughter knows who she is, and asked for a photo.
All equally as plausible as her dating Goff, pending further evidence of course.