It’s possible. Just having any disabling disease can cause anger. Saying hurtful things can also be an MS disease symptom, like depression and mood swings. To me Samantha’s rants seem more planned than spontaneous. But who knows?
Disinhibition is one symptom some suffer:
Normal consideration for others, awareness of others’ feelings and the usual sense of decency may disappear. For example, someone may make hurtful or totally inap- propriate remarks in a way they would never have done before;
https://www.eurims.org/images/stories/documents/SIG/Psychology/RIMS_Personality.pdf
Disinhibition is one of the rarest behavioural symptoms of MS and only a very small percentage of people are affected. It is linked to MS-related damage in the brain.
People experiencing disinhibition lose control over their impulses, leading to inappropriate behaviour and a loss of their sense of social rules. They may have little or no awareness of others' feelings regarding their actions.
For example, someone may make a hurtful or inappropriate comment, break into a rage, or behave in a sexually disinhibited manner – all of which they would have considered outrageous previously. It is important to recognise that people experiencing this symptom cannot control their behaviour.
Other mood and behaviour changes
