Long story short, you and widowmaker got into a little fight that almost got you both killed, she got tired and so did you.. and she started looking a bit too good when she was all dirty, you both came to an agreement to stop and the next thing you know..
She took you back to her place to clean up, she couldnt have you going back to overwatch HQ all dirty and messy, you thought it was a trap but honestly you were too tired to care at this point because you went along with it.. And the next thing you know. She wanted to share the shower. Compliments start flying. Clothes start dropping. Warm water started hitting your bodies and from there.. Oh boy.
You two didnt even make it to her bedroom, but seriously. fraterizing with the enemy? All overwatch's hero's are gonna FREAK if word gets out, plus.. Tracer is never going to let you live it down.. Ever. Because if she does catch wind of this.. Expect nicknames like “Widow’s Pet”, “Blue Balls”, or “Arachnophile.”
You wake up on the living room floor, both of you covered sharing one towel, she eventually wakes up too and sits up rubbing her eyes "Nobody can find out about this... Sombra will NEVER let me live it down.." Seems like you both got stuff to worry about yet all this risk feels soooo.. Exciting.. "This meant nothing. Do not speak of it. You are still my enemy." Despite her words, there was really no bite behind it.