My 7 yr old broke her arm/elbow last yr & once again she cracked the same elbow should I b concerned? Could she have a problem with her bones?

Not unusual. Kids who are physicly active occasoinally fall & get simple or complex injuries to arms or legs that are more a reflection of their coordination than the quality of bone structure. A simple review of her xrays is often adequate screening for the quality of her bone density. The kids i've seen with bone issues all came to light before they walked.
7 year olds. It is the nature of kids around the age of 7 to be very active and to have falls and other adventures. Thus the mere fact of 2 fractures around this age is not a special reason for high concern. It is possible that the last fracture left the spot on the arm a little weak and thus easier to break, but that is unusual in kids. What i would do this time is to check an x-ray after this fracture heals.