And it starts with a list of options, three of which are some flavor of "goodbye" and one line that I (PERSONALLY, I know this is not true for everyone) can only imagine being delivered with a husky voice and squinty bedroom eyes. I know Bioware flirting is always awkward, but I have a hard time reading anything legitimately romantic into it. If she was into him for some reason besides the physical, there's no way to express it.
Besides, the Mages in the student's quarter will comment on how obvious Cullen's crush on FMage is to everybody. This makes less sense of FMage has been throwing these do-me-now kind of lines at Cullen. If she's this not-subtle, then how is SHE not the story that's going around the tower? If she'll proposition him right there in the hallway, how is it everyone from Gregoir on down isn't telling her off for harassment?
Dude, you really took that one post I said where I didn't care for Cullen x Amell/Surana because I felt it could never be a truly equal or consensual relationship since one person (the Templar) has all the power and the other (the mage) doesn't really have any power, and ran with it.
Only, instead you keep taking every opportunity to blame and sl*t-shame Amell/Surana.
Cullen has a crush on Amell/Surana. That's not their fault. Considering he's stated to have that crush on you before you can even react to him and/or whether your character shows they like him, dislike him, don't know him from a brick in the wall, etc. one can infer that he grew to like the Mage Warden even though/if she did nothing to court his attention.
And that's just it: you seem to assume that just because he likes her and/or the player has the option to flirt with him, it must be because she was throwing herself at him. I'm sorry, but that's a sexist assumption. Just because a guy likes a girl doesn't mean it's because she threw herself at him. Sometimes people come by their crushes honestly, whether or not the other person noticed or courted their attention.
Regarding the flirt dialogue: while the player has the option to proposition him, due to the lack of voiced dialogue or body animations we don't know the tone of voice she uses or how loudly she says it. You imagine her yelling it in a husky voice while jutting out her hips with "do me" eyes, but plenty of other people imagine it differently. She might say it quietly, softly, sweetly, playfully, etc. Cullen is so skittish and nervous when you come up to him, even if you just say, " 'sup?" that his extreme reaction (read:bolting) is not "proof" that she was obviously going full Jessica Rabbit on his d!ck. Also, just because she can flirt with him that one time doesn't mean she's flirted with him before.
As for why Cullen is famous for being in love with Amell/Surana rather than the other way around, again a) Cullen is shown to like Amell/Surana before she can show whether or not she even likes him, b ) he's obviously bad at hiding it. You've seen how differently he acts from the male mage verses the female mage, and even Jowan verses Amell/Surana. If he can turn into a fumbling, stuttering mess just from her walking up to him, it's safe to assume he probably gets starry eyed even when she's not looking, so everyone probably caught wind and started passing it around. Again, just because he likes her doesn't mean it's because she was wantonly seducing him.
I'll admit I don't approve of Circle Templar/mage relations (because I just really don't think a truly equal, consensual relationship can form between a jailer and prisoner), but I'm not going to jump to assume the potential relationship was because the mage (especially female mage) was this cartoonishly wanton, husky, deviant sex demon trying to ensnare an innocent little (male) Templar with her evil womanly wiles.