I watched your video and it looked like a normal feeding to me! It does take them a little while to get it down but she does look small for her age! I would feed every 3 to 4 days to get her weight up. There is nothing wrong with feeding live. I feed all mine live and in the wild they eat live. Also you don't need to feed in seperate container, you will find that you get a better feeding response if left in their tank. Young snakes eat alot! I would go with at least an adult mouse! Give us some pics of your setup and we can see if there is anything we can suggest to make your snake happier!