The amount of frames is wholely dependant on how long you want the walking cycle to be. There aren't any rules on how many frames they have to be, because everyone walks at different speeds, in different ways. This is why I brought up the question of frame rate.
In animation (film in general, but I'll be discussing animation), you have a frame rate, which is the number of frames which play per second. Standards are 24, 30, and 60. The more frames you have per second, the more fluid you can animate motion.
So how many frames your walking cycle is depends on the two key factors of how long you want your walk cycle to be in seconds, and what your frame rate is set to. If you want to see how long your walk cycle is, start walking at a very steady speed, then at some point when one of your feet touches the ground, start a timer. Count every step that follows that initial one (Don't count the step you start the timer on), and when you reach the 10th step immediately stop your timer. Divide the time you got by 5, and that's your average walk cycle time. Then divide that tike by your frame rate, and that's the number of frames you would need to animate your particular walk cycle at whichever frame rate you chose.
Also, Photoshop isn't a very good application for animation at all. It has a couple features for making gifs, but overall it isn't exactly a tool for animation. If you like Adobe, consider trying Adobe Flash (or whatever they're calling Flash nowadays). You'll find it more similar to illustrator than to photoshop though, since it's vector-based, but it is a tool for animation that's been around for a while now and is a common choice for beginners due to its simplicity. Otherwise, I recommend googling "2D animation software" and using a free trial of something to see if you like it.
If you're still looking for critiques on your current walk cycle, consider having the android take slightly shorter steps, and don't have her body bend down quite so much with each step. Everything is just a little too exaggerated. You're certainly getting closer to a standard human walk! I'm sure if you told someone "this is my first attempt at animation," you would make a number of people jealous of your skill.
