Thanks truthseeker.
What are the circumtances under which someone can be sectioned?
In my (limited) experience in this area I have found that sectioning someone is not as easy as one might think.
If this lady lives alone she has presumably (to this point) been able to eat and stay warm (ie, she is not on the street or dead) its quite possible that she just needs some support from social services (a home help or meals on wheels etc...) to be able to carry on.
If the lady does not live alone then I suppose its a question of whether or not whoever is caring for her IS actually caring for her.
If the lady is coherent enough to make decisions (even though they may not be in her own best interests) there is a good chance she can insist she is happy as things are and that she wants people to leave her alone.
Really the public health nurse is a good first place to call, you can explain the situation and let her know the guards have been involved. The guards will probably assign a social worker who can liase with the public health nurse. Hopefully that will help bring some resolve to the situation.
You dont mention if there are other people there who should be helping out, or if there are any regular visitors.
Another option that I have used in the past is letting the parish priest know, he could hopefully call and then he would also be someone who might consider getting onto social services.
I appreciate that you would like to see this situation sorted, and you are to be commended for that, but be aware - the neighbours family may resent interference (even with good intention), and it is extremely difficult to get good practical help from social services in certain situations (or at least this has been my experience).