How do I retrain my cat to not want to go outdoors?

[tamara m]

I have adopted a 4 yr female cat recently. She spent the first 3 years of her life as an indoor cat, then she was able to spend times indoors and outdoors. I am in a busy neighbourhood and am not in the position to let her outside. She is whining and crying to be allowed outside. I've always kept my cats indoors to be safe. I feel guilty. I could let her out supervised on a harness and tie-out but she will want to stay outside as long as she wants. And I'm worried about fleas and confrontations with neighbourhood animals. Does anyone have any experience in this area? thank you