Should I have my female rabbit spayed?

My rabbit, Daisy, Is coming up to about 11 months old now, and we think she is in heat. She seems a bit less lively than she normally is. We are not sure weather to have her spayed, as she is an only rabbit and isn't one bit aggressive she hasn't bitten anyone once! She has a very docile temprement. People say that if they are not spayed then they can develop cancer. What are the chances of this happening to our Daisy. And is the operation risky, she has been through 1 operation before so we think she would survive it, but its weather or not we want to put her through it. Also, is it best for them to have 1 litter, as a friend told us it was. We think she would be an amazing mum but we are very very confused! :) Thanks :)