How to deal with someone who will not take their meds?

My 96 year old mother, who suffers from severe dementia, has started to refuse her bedtime medicine. It has become a very nasty ordeal for both of us. She typically will take her morning meds without any problem, but because her aggressive behavior kicks in sometime in the late afternoon, by the time her bedtime arrives, she is out of control. She kicks, spits the pills out and tosses the water in my face. We do have her on a small dose of Zyprexa in the afternoon to take the edge off of her behavior a bit, but that seems to do little if anything to calm her down. This does not appear to be a problem with swallowing as her appetite is still fairly good and she has no trouble swallowing when eating. I have tried everything, including crushing the pills up and/or serving with applesauce or pudding and she will still hide the pills in her mouth and spit them out later. I've already cut out some pills (with the doctor's blessing) but we are now left with the critical ones that she absolutely needs. Has anyone found a way to deal with something like this? I can handle every other challenge she throws my way, but I am stumped on this one as I can't just say "Ok, never mind, you don't have to take your pills".