I should put less in the bowl and empty it out and refill it every other day, whether it has been eaten or not (for some strange reason I find our hamster ignores old food but is more interested when it's straight from the packet so it must smell fresher or something).
I put about a tablespoonful out for our hamster. A Uk tablespoon is about 20mls - a measuring tablespoon (US) is 15mls. So 30mls sounds quite a lot.
Sometimes they have such a big hoard they don't bother to pouch for some days - especially if you've been feeding her by hand in between.
Of course if you put less in she might empty the bowl every day in a panic that there is a good shortage lol! I put a huge bowl of food out for our hamster when we went away for 3 days and I don't think he touched it! He didn't seem to like it being so full - maybe it's hard to get to the tasty bits that fall to the bottom if it's too full, I don't know!
Hamsters don't eat a lot anyway - very small amounts, but she might be eating more than you think as they often snack in bed from their hoard.
Just wanted to say it isn't really necessary to clean the cage once a week - cleaning can stress them a bit. You can spot clean and do cage cleans less often, especially if you use a litter tray. I like Erin's Hamster's cage cleaning tips video - it's worth a look - I now only do partial cleans and less often
https://www.youtube.com/watch?v=5jVnEjrXbww