If there is a mental condition that led to her outburst, I'd be surprised if it's the first time it's happened at a meeting (in her 40 years).
One thing I notice about my special needs teens at school is that they always tend to waut til theyre back in a safe place before they have a good old blow-up. Preferably with people that they trust most. I don't think it at all surprising that often people hold their frustration in until they get to their safe place - often their home group.
If it was just a little yelling and swearing I suspect that once everyone has calmed down, compassion will win out.