Sheila couldn't get off sofa's without help. Source aleady supplied.
Sheila walked down to see Jeremy in the fields the afternoon before the murders so she wasn't completely incapacitated. Think any difficulties she may have had have been highly exaggerated.
We don't know if she had any problems with her movements at that time. Personally I doubt it.
Haloperidol CAN cause muscle twitches, stiffness and facial gurning but this usually occurs in older people who have taken it for a long time ie. years. There is a possibility that there may be some muscle twitching in short term, low level doses but it's much more unusual.
I know there have been a few references by friends and AE to her having difficulties but these were mainly in the past when she was taking Stelazine rather than Haloperidol. She had been prescribed meds which would help with such problems but we know from her autopsy that she had only been taking Haloperidol which makes me think she was free of symptoms at that time.
I wouldn't think for a minute that someone like Sheila who minded so much about her appearance would not bother to take tablets which could stop these very unattractive side effects if they were happening..