You nailed her shape right away, and the colouring fit her perfectly
Only thing im a bit... well... uncomfy with is: the eyes. Or more precisely: the direction of the eyes. Tho the glowy sphere in front of her distracting a bit from it, it looks like her right eye (for us on the left) is either pointing up a bit too much or her pupil (same eye) is a bit too small. Last case is the more likely, if i look at the size of her iris. To me, as i have to deal with issues all around the eye for my living, it looks a bit like she has a minor Hypertropia [link] (vertical upwads squint error) or a pupil offset on the right eye. And it's not a matter of perspective. Even turning or tilting her in any direction would make no effect.
First Pokemon? Dang, this is great! Good choice of Pokemon too (I love Mew). If you ever get motivated to draw some more Pokemon, then I say go for it! Would really love to see some others done in your style.