hi there, im so sorry to hear that your mum is poorly =(

Each time i have had a shunt malfunction, I had no evidence of there being any problems from the tests that were done. which included
numerous CT scans.
Shunt series.
ICP monitoring
Shunt tap etc.

I was admitted to hospital after the opthamologist found pressure on my optic nerve, which was completely unexpected as i felt fine for weeks and weeks. So i was fitted with a ICP monitor the next day...whilst under surgery for that, they tapped my shunt, i had no pressure and no infection.
But hours after that surgery, i showed the physical sides of shunt malfunction, vomiting, irritability, photophoebia, headache, gripping shunt pains, then gradually lost conciousness and my heart rate fell to 35bpm!! which is well past resuscitation rate according to nurses. When this happened, it was obviously signs of shunt malfunction, this is when i was rushed to a emergency CT scan of my head, which quite rightly should have shown pressure or change. it didnt, atall.
I was taken into emergency surgery and the only evidence that there was pressure was the fact that when they drilled the burr hole, fluid flew metres across the theatre at a pulsing rate, where it was at such high pressure.:O

Im telling you, your mother and you know when its a shunt problem, its your gut instinct, each time i was ruled out for my problem being shunt related i knew it was infact the shunt!
&& well those problems resembled that day i went into the coma state. But believe me, you will know.

My hopes are with you and hope your mother gets sorted out real soon, i wish her the best of luck in getting well. =) stay strong.