About Heather, she has always been a bitch to MC, and the last episode was no different. Only now she is using him against Tommy. Because the MC is now one of the Diks, he gets close to Tommy, even knows how to fight.
If the MC fucks Heather, it will hurt Tommy a lot, MC and Tommy's relationship is ruined, The Brotherhood will also be damaged. But for Heather it's just collateral damage, but she does not mind, maybe even glad for the extra damage. Nothing new, standard female revenge, ruthless and cruel.
I didn't touch that crazy bitch in any of my playthroughs. But if you fuck Heather, too bad for you