In my personal experience, I learned that English medicine IS effective but with many uncleared doubts about the after effects. It also gives quick relief from your pain, but it may only be temporary. This is why I chose the safer alternative medicine, Ayurveda.
Whatever be the method of treatment you follow, Ayurveda, Siddha or Unani, the physician should have a great reputation. In the past I had not had much success with Ayurveda too, so you can see that a lot depends on the doctor who treats you.
Recently I saw a friend's mother transform from a bed-ridden state to a moderately active state within a period of 2 to 3 months and decided to see her doctor. And I wasn't disappointed. Now I have started recommending his name to my friends and family.
So make sure that you are seeking the advice of a good practitioner. This can be done only with the help of recommendations from friends and acquaintances. I am not familiar with Siddha, so am not able to tell you much about it. But if your doctor doesn't tell you about your condition, medicines etc., that is not a good sign.
You should ask the doctor for all details regarding your condition and if you don't get adequate response, should change the doctor. This is my opinion.
Best wishes for your mother to get a grip of her condition and manage it well. Drinking lots of water is very helpful.