I have taken her to the vet however they said it was to early to operate,so I have to wait until it get a bit bigger.just wondering if their was any other way to help her meanwhile??

Is she in pain? Is she not eating? Usually tumors are not painful, unless it is effecting her organs or preventing her from seeing or eating or using the bathroom. So where exactly is the tumor located? What did your vet tell you?

The vet said it's too small to remove? That makes no sense.

I would go to a different vet and get a second opinion. Waiting until the tumor is bigger isn't logical. That would be like telling a woman with a lump in her breast to wait until it's bigger to remove it. By that time, if it is cancerous, the cancer will have spread.

The time to remove a tumor is when you find the tumor.

Find a different vet.

There is nothing you can do for your rats tumor. I was a veterinary technician for 12 years and I also had my own pet rat (they are the best pets) It is common for rats to get tumors with age. The maximum a rat can live is about 3 years and more often than not, cancer is the killer.
Don't do anything yourself, you may hurt your dear pet. Try another vet.