Hm, no you guys are getting it all WRONG. You're paying way too much attention to the fact that Cloud and Tifa live together with Marlene and Denzel as a family.
Cloud, you see, is a jackass who doesn't mind living with Tifa, a woman who is in love with him, even though he clearly doesn't give a fig about her.
Or, wait, wait, I've got it - Tifa
doesn't care about Cloud - she's actually secretly in love with Barret, which is why she cares so much about Marlene. She's actually pissed off that Barret left her and went off gallivanting the planet in search of monsters/a new arm/weed, so in true sisterly fashion, she takes it out on her little brother Cloud by nagging at him throughout AC/C.
Bah.
I actually like Tifa... She wears a short skirt, so what? Stating that she is a slut based on her clothing is just...
Tifa
did care about Cloud for years. She was looking for news of Cloud in the papers, she even asked Zack whether he knew a blond guy in SOLDIER and then begged him not to tell anyone she asked.
She meets him years later - and right off he says something that makes her wonder what's wrong with his head.
Tifa obviously wanted to keep an eye on Cloud, and her feelings for him were reawakening, if they'd died down at all. On top of that, Aerith turned up. Tifa wasn't only battling her feelings for Cloud AND the appearance of a rival (who she liked as a friend) -
she also had to worry about Cloud's strange memories.
Excuse her for not kicking Aerith in the ass and hauling Cloud off to bed.
Even though it galled her, she seemed to be more concerned with Cloud's mentality than in trying to stake a claim as his girlfriend.
She also decided to stay behind in Medeel to look after Vege-Cloud. She gave up looking to combat Sephiroth and Meteor, and saving the world, to stay
with the guy she loved.
Then they clear up the mystery of his incongruous memories and Cloud is himself again. They're off to a do-or-die attempt to save the world, and quite frankly to them it probably looked like they'd get eaten up by Sephiroth or crushed by Meteor. Chances of survival probably looked slim. So, as has been pointed out before, I'm wondering what on Gaia is wrong with Tifa sleeping with Cloud in such a situation!!
It had nothing to do with the fact that it happened after Aerith died.