my GF did thesame thing and i know how frustrating it can be.heres my advice: most girls dont like the facial thing for the same reason that lots wont swallow. this is because they have grown up thinking that it is disgusting. you say that she swallows your cum so she's allready pretty at ease with the white stuf. she is probably self concious because people can see her face. sounds silly dosnt it. anyway, try having sex with her and pulling out in time to shoot your load on her stomach. then gradualy move up to her tits. try getting her to wank you off over her tits, so that she feels in control. then "axidentaly" let some splash on her face. But, dont sit there all smug because you hit your target, slowly wipe it off for her, nice and sensual like. or if you can handle it, lick it off, she swallows, why shouldnt you
also, give her a reward, slowly lick her tits and stomack. the insides of her thighs and then eat her out. Over time she will associate the cum on her face with pleasure and loose her inhabitions.