My three year female rottweiler has never shown any aggression until this year. She has always been very sweet, submissive and patient with my children but is starting to shown intolerance and aggression. She has bit my daughter on the arm but did not break the skin (we thought that she was just playing). Then she bit my husband's food pretty hard when he tried to get her to move by nudging her. We are in love with her but do not want to risk this with our children. She is going into heat and I wonder if she is just "moody" or don't feel well. What do you think?