Letrozole and Bruising

My mother is almost 4 years post surgery. She had a lumpectomy and lymph nodes removed from under her arm. She has been taking Cipla every day as advised. She checks herself daily and has had no problems. However today whilst checking herself she noticed some bruising under her arm where the lymph nodes were removed. Obviously this caused her some anxiety. She did tell me that she had moved some furniture down stairs on her own yesterday. Could this be the cause of the bruising?