Uhmmm, doesn't her legs look really short in both pictures? Or am I just issing something? But anyway, really great change in just few months! You were great even back then but you have still gotten LOT better!
I can totally understand your sudden improvement because I actually went through the same thing ^^ I started digital work in late May. It's September now and I must say, I'm shocked myself to see improvements in everything. I guess the advice for everyone else is that the best way to get improvements on your work, is DRAW EVERYTHING. And draw a lot. Learn a lot. Watch tutorials. And you'll see results eventually ^^
But anyway, again. This is great! It's always nice to see good digital pieces