Aherne pissed off to Australia, last I heard. She went through a bitter & public divorce, turned to the bottle and had several breakdowns afterward. She is, by all accounts, a difficult & volatile person.
I'd say it's more to do with her personal problems than being anything else.
As for the show - the first series was good, but in my opinion sucked thereafter. It was catchphrase humour, and that can really only be taken so far. I see little point in a reunion tour, other than the members have run out of work, and have decided to thrash the cash-cow with the proverbial stick one more time.