What mixes have you tried her with? Have you tried the bunny dream expert from zooplus?
Bunny Dwarf HamsterDream Expert | Free P&P on orders £29+ at zooplus!
Mixing up your own food is really quite an involved process as you need to make sure you are balancing all the nutritional values. There is a thread on the forum which would be worth reading if you were looking to make your own. I've linked it for you.
Has anyone ever made their own hamster food?