Loss of sensation is a common problem in people with diabetes. The disease affects circulation and blood supply to the hands and especially the feet. The first time numbness develops, it can be very anxiety producing.
As a nonmedical person yourself, it may not have occurred to you to look for other tell-tale symptoms of a problem that suggests immediate need for medical care. For example, fever, sweats, or nausea might signal an infection. Redness, swelling, blistering, or oozing of pus from the toe(s) would also be a red flag requiring medical attention.
You did the best you could under the circumstances. If you think there might be future times when you will be called upon to aid this person, it might be a good idea to get some information ahead of time. For example, keep handy contact information for her closest family members and her primary care physician.
Check your community for other (lower cost) options for those late night or weekend emergencies. Some hospitals have a 24-7 nursing service you can call with any medical or health-related questions. Some cities have local walk-in clinics that charge a single (pay upfront) fee and take care of any immediate problems. They are better trained and equipped to know when to send you/your neighbor to the emergency department or to seek more specialized services.
But to get back to the original problem, numbness in the feet of someone with diabetes does require diagnosis and management. Without proper sensation, it is easy to stub the toe, cut the skin, and develop a serious infection that could lead to amputation for this patient population.
An emergency room visit might not have been needed for this particular problem. But at least this visit will aid your neighbor in getting the proper education and treatment she needs. The first appearance of numbness is certainly a signal that further management is appropriate to prevent more serious problems from developing later.