Doors and Windows - window in bath

Ok....i had a tiled wall surround and it was old and ugly so i decided to replace it with a vinyl surround.

I removed the walls and the tub and did the plumbing all new and put in a new tub

The issue is this. The home had aluminum windows when i moved in which i had replaced with vinyl windows. There is a window in the bath and the sill was not level and leaked. There is no way i can level the sill (or tilt it in for that matter) w/o removing the window which is not an option.

I am faced with having about 1/2" of space at the bottom and both sides of the window i need to cover. I was thinking of tiling it but I'm not sure that will work. I have seen trim kits that some of the surround companies make but i dont think that will work because it is such a small depth.

anyone have any ideas or is tile my best bet?

Could you use some type of 1/2 round wood trim to go around it?

Did you replace the greenboard behind the wall surround? There's your half inch if you didn't. Your post didn't say that you did.