Remember the 11th Hour where she basically stared at the doctor whilst he got nekkid with a wry smile on her face? It's pretty much implied from the start that she has sexual feelings for him, which isn't really surprising given he was probably her first love (even before she was aware of her sexuality he was a fantasy figure in her life so who knows how she started to view him once puberty began.)
As for the catalyst, the catalyst was that she'd just almost died, and as a result got extremely horny! All her fears and fantasies merged togeather at that one point. Traumatic situations have strange effects on people (just check out birthrates 9 months after major disasters/incidents!)
I know people like to equate sex with love, but you have to accept that not everyone sees it this way, and many can seperate the physical and emotional acts, which is clearly what Amy was doing there; she didn't profess her great love for the Doctor, or say she wanted to marry him, she just wanted a shag right there at that minute, having survived death at the hands of the angels, with the man she'd been fantasising about in myriad ways since she was a small child, on the eve of her wedding to a man she clearly loves but just isn't sure she loves enough, or that she wants to bind herself to him and Ledworth for life.
In many respects at that moment Amy is probably the most realistic companion we've ever had: flawed, scared, horny, confused. She's a flirty individual, maybe too flirty at times, and Rory has clearly been a bit of a doormat in their relationship (although you can almost imagine that at times he must be the one that wears the trousers, the sensible practical one).
Agreed! Exactly what I'm saying. Amy wanted to get laid. Nothing more, nothing less. She is being portrayed as a realistic girl, rather than a soap opera romance figure ala' Rose/Martha/Most any woman that met the Doctor during RTD's era. There's nothing in Season Five to suggest otherwise. She implicitly stated that she wasn't interested in The Doc for anything more than to get some. There's no other option to accept the moment than how it's written. Otherwise, it's just the viewer making up fantasies and Slash-FanFics about romance and "love" for their own satisfaction.
The "getting laid" scene is the moment I fell in love with Amy. It's the moment she stopped being a written character and became a real, imperfect, lustful, irrational human being like the rest of us. Clearly, the single most believable female character written for Doctor Who since...ever.
