It happens rarely. May occur with long-term use.

Sometimes, light blee­ding around menstruation can happen due to implantation. This is whe­n a fertilized egg attache­s to the uterus lining. Not eve­ryone experie­nces implantation bleeding, but it's possible­. No need to worry exce­ssively. However, if unce­rtain, take a pregnancy test for re­assurance. Stress also impacts menstrual cycle­s. 

In some cases, doctors may refuse hysterectomy due to ethical or moral objections like in sterilization surgeries. Some doctors may also be bound by institutional or legal guidelines that restrict certain surgeries based on age, medical necessity, or other factors.

Since you had a delay in your monthly period, it may be a sign of pregnancy, but there are other possible reasons particularly stress and changes in hormones. To know that you are safe you could do the test only after the 14th of May and learn if you are expecting. Your cycle is subject to the effect of countless factors in various states of your body.

It could be because of several factors that include stress, change in weight or hormonal disturbances if your fiancée has missed her menstrual cycle. But the main reason is pregnancy. A test should be conducted to determine whether she is pregnant or not. Further assessment and treatment should be discussed with a gynecologist.