I grew violets in a South facing window for years with no problem. Just make sure that the violet is far enough away from the window so that it doesn't get excess heat in the summer. Across the room will be too far away.

If you want to locate your plant across the room, position a spiral fluorescent bulb in a desklamp to give it adequate light during the day.

Master the watering of your plant before trying any fertilizer. I've had good success with various African Violet fertilizers, with or without urea. Just a touch will do you ...

Other tips ...

Over-watering is the number 1 killer of African Violets.

Never let your Violet become waterlogged. Make sure that the pot has adequate drainage (holes) so that excess water can be discarded. Only water when the soil has become dry to the touch.

Don't OVERPOT your plant. Violets BLOOM and grow better when their in pots no more than 1/3 of their foliage diameter. That's usually a 4" diameter pot, at most.

If your violet is 6" across, it needs no more than a 2" diameter pot. Anything more, and it will spend months trying to fill the pot with roots INSTEAD OF BLOOMING.

Lighten the consistency of your soil by mixing it with a like amount of perlite. Violets prefer a light, airy soil. Perlite will lighten it up.