Am over or under feeding my pup?

I want this border Collie to be able to take down a great Dane so I have to bulk her up quick!

Anyway she's a border Collie. 6ish months old. I've been giving her a little under a cup of food twice a day. Sometimes she acts like she hasn't been feed in weeks. Also, if you took the great Dane partseriously we can't be friends.