I have that same one, love it! Yours looks better than most Begonias at my house of any type, (besides the wax ones that actually seem to like winter.) In the 2nd pic you just added, that IS more light. If my Begs saw that pic, they would be jealous! Obviously a better spot/window, and probably more hours of sunshine at your place this winter.
I can tell the difference of all of the missing sun here this winter because last winter at this time, rhizomatous Begs were full of beautiful leaves, making flower stalks. This year I'm not even sure they're all still alive, same spots, same care, repotted before coming in like last time.
