Bella's already had two heat cycles, right? By getting her spayed before she has her third cycle, you can still reduce her risk of mammary cancer to 26%. If she has that third cycle, her risk of cancer probably won't be reduced by spaying her.
So save, save, save!
If a female dog is spayed before her first heat cycle, her risk of developing breast cancer is only 0.05%. If she is spayed after having only one heat cycle, her risk of breast cancer jumps to 8%. If she is spayed after her second heat cycle, that risk becomes 26%... that's more than 1 in 4! Spaying a dog after her third heat cycle may reduce the risk of mammary carcinoma (breast cancer) but not appreciably. The take-home message: intact female dogs are 50 times more likely to get breast cancer than a dog spayed prior to her first heat cycle. Ogilvie, Moore. Managing the Veterinary Cancer Patient: a practice manual. 1995