You are right to be concerned. Falling is a major cause of injuries and even death in adults over the age of 65. Tripping over objects is the biggest cause of falls in this age group.

Studies show there are other factors at work here, too. Vision is important but there are different kinds of vision in this task. Visual acuity helps the person see the object. Depth perception helps us gauge the distance between the object and us.

And finally, contrast sensitivity is important. Contrast sensitivity allows the person to see the end of one surface and the start of another. For example some older adults are unable to tell when floor tiles end and the bathtub begins in a bathroom. Stumbling and loss of balance can occur at boundary changes.

Each part of vision is only part of the picture. The person must have quick enough reaction time to safely avoid the object. Reaction time is tied to muscle strength, joint position sense, and neuromuscular reflexes.

It may be a good idea to have a physical exam with a medical doctor. If there's no medical reason for her difficulty avoiding objects, then a physical therapy program of balance, flexibility, and strengthening exercises may be helpful.