Absolutely, and though I'm not convinced as Maggie said that Colin was right there is more on the side effects of Haldoperidol here:
Muscle spasms: It is relatively common to experience muscle spasms on this medication. It is an older antipsychotic that is associated with development of extrapyramidal symptoms. If you notice more frequent and uncontrolled spasms, talk to your doctor about it. Muscle spasms can often be a precursor to tardive dyskinesia.
H Steve, I wouldn't argue with Colin as obviously he has more knowledge than most about Sheila's physical health however there are different grades of TD. I keep meaning to find Colin's comments on this but haven't gt there yet.
I know Sheila took Stelazine for a while which was an old drug very well known to cause TD and I have it in my head that she was also prescribed a drug which prevented or controlled TD but need to find the details on the forum. We do know that Shela wasn't taking a drug for TD at the time of her death as it wasn't present in her body which would question the fact that she still suffered from TD.

We don't know whether changing from Stelazine to Haloperidol helped her or made it worse and may have been the reason she wanted the dose cut down.
Imo we just don't know for sure if Sheila was suffering from TD at the time of the murders, I agree if she was and it affected her upper body she would have found it very difficult to handle a firearm.
I have seen TD of the face and it is an awful affliction which Sheila would have absolutely hated and I'm sure she would have tried anything to get rid of it.
The side effects of the medication Sheila had to take were horrendous and she may have believed they were worse than her illness and to her may have felt like a fate worse than death.