Hello! I had gone through your query and understand your concern. A bruise is a traumatic injury of the soft tissues that results in breakage of the local capillaries and leakage of red blood cells. Easy bruising can occur when the blood vessels are weakened by diseases, medications (such as aspirin, prednisone and prednisolone), and aging. Since she is taking blood thinners It is possible that a very insignificant injury could have caused an obvious hematoma (bruising). You can put some cold in her foot . If she can move easily her foot,doesn t have strong pain,or other complains you don t need to worry,she will be fine. If her foot is really swollen,hurts a lot and she can t move it than I suggest to consult a physician for further diagnosis or treatment. Hope my answer has helped. Take care Dr.Rovena