Liar Birds by Lucy Fitzgerald

Oonagh, Rose and Teresa really only took one thing seriously - having fun.  At school they had enjoyed upsetting the nuns by deliberately sticking up for abortion, homosexuals, and Sinead O'Connor, and wearing their school skirts either too long or too short. 

Big time girls in the small town of Ballycanty, they relieved the monotony of their lives by repeating gossip, and when there wasn't any, by making it up.  And when one of them heard that someone in town had an unmentionable disease, well, it was too much of a temptation not to embroider the story a little, just to make it more exciting.

It was Teresa on whom the gossip would backfire.  And when her fast-living sister turned up from England amidst a positive welter of rumours, Teresa found life exploding round her.

Suddenly 'having fun' was no longer enough and as sadness touched her life for the first time she grew increasingly disturbed - about her friends, sex, the Church, and indeed her whole life.At the end of that burning summer, Teresa faced up to some painful decisions and decided that things must change.