You are right to be concerned. Falls are not a normal consequence of aging and the research evidence tells us a history of falling is a good indication of a
heightened risk for additional falls. We also know sooner or later repeated falls will result in an injury.
There are a number of possible reasons for someone to suddenly begin falling. Fortunately, most of them can be modified to reduce the risk of future falling. It would however be best to encourage your friend to visit her primary care provider for a physical assessment that includes as a minimum: balance and gait, medications and vision all of which can cause of falls.
For additional information the CDC offers a nice brochure entitled What YOU Can Do To Prevent Falls that addresses the more common risk factors for falling.
Meanwhile, if you and your friend can think about the circumstances of those fall events it can also help to pin point the cause and to facilitate a constructive dialogue with the health care provider.
In addition, making some modifications to the home can enhance our day to day safety in an environment where we often feel the safest, yet up to 60% of falls occur in our own homes. Look to the CDC for a brochure on home safety Check For Safety: A Home Fall Prevention Checklist for Older Adults. It offers both a simple checklist and suggestions for improvement. (I would recommend that readers at any age use the checklist to assess their own homes).
Finally, the outdoor environment is often risky as well with uneven pavement and all sorts of natural tripping hazards. Being a little more alert to environmental hazards and reminding your friend to let her eyes adjust when going from the bright outdoors to darkened interiors or when wearing darkened eyeglasses inside can be helpful.
Fall prevention strategies apply at any age. We want to keep everyone safe from preventable falls active in the community for years to come and hope that these suggestions have been useful.