Biopsy Not Done

Today's my mom's appointment for biopsy. My mom was sent back without doing the procedure. Turned out that the Dr forgot to tell her to stop her warfarin so they couldn't proceed. It totally slipped my mind as well. So Jeff helped me call the clinic & Dr to discuss what's the course of action to be taken. He decided not to proceed with the biopsy but instead do an ultrasound 3 months later. I'm worried... If it's cancer, is 3 months too long to wait?