Matt
Whilst I’m sorry to hear about the demise of your friend’s cat, I can’t see why you think that suing the Owners Corporation would be a reasonable option.
It seems that both animals were on common property without any form of control or supervision. If I had a fight with my neighbour on common property, and lost out, having to fork out for medical expenses as a result, would you think it fair and reasonable that I sue the owners corporation to recover my costs (+presumably the lawyers fees?)
What was the Owners Corporation able to do to prevent this animal attack. Should they have had a guard on duty 24/7 watching over every square inch of common property so that they could intervene?
If your friend wants to seek to amend the by-laws to prevent dogs being allowed that is their prerogative. But why penalise those dog owners who are responsible and keep their dogs on a leash and under control when on common property?