Her lover comes in.

The woman pulls away and blushes. "Uh, hi. Why the he'll did you blow me just now?" she asks, staggeringly confused. You laugh, the strong woman you saw when you walked in was gone. Replaced by a shy and timid shemale.
"'Cause your cock looked irresistible." She is taken by surprise, mainly by the fact you said it so nonchalantly.
"W-well, I-I have a g-girl f-friend!" Her tan face becoming red as a barn.
"Ooh," you shake your head, "She won't like that you got blown by your roommate you've just met."
She gasps a little, mouth agape. "You were the one that walked on in here and sucked me off!" her face continues to blush as she realized what she yelled. The sound of keys jingling and falling to the floor is heard by you and te tan beauty. Both of your heads turn, seeing a pair of eyes staring at you.
If you could look through the eyes of the woman, you would first notice your girlfriend and some other girl with their cocks out. You would also see wet cum riding down from your girlfriends cock and the girls mouth. It didn't take a rocket scientist to figure out what happened here. And if you were her, you would have flown into a rage! Which she did.
"What the fuck is going on here!" A rhetorical question, of coarse she knew. Again doesn't take a scientist.
"I can explain!" the other shemale starts, then quickens so she is not interrupted. " I theorems it would be kinky if when you came home you saw me naked and we would make love so I took off my clothes and waited then this girl came in and I thought is it was you and she blew me and that's all we did before I realized it wasn't you and then you came home and now your mad and I am sorry." she ends this tirade with a large gasp of air.
The girl stood there speechless, thinking of it all. "Fuck, that's hot." she says forgiving her lover, "Still have a round left in you?"