YANBU. In fact no one is asking them to perform/be present at the abortion, but to provide pre/after care.
It shouldn't be up to nurses to pick and chose what surgical procedure they will take part in. If someone won't undertake a clinical procedure that is sanctioned by law and provided by the NHS, they should think long and hard about their choice to become a nurse/midwife.
How much shrift would (an atheist) teetotal nurse get if she refused to treat someone injured as a result of drinking?
Or a vegetarian nurse who refused to treat someone who'd got food poisoning from eating dodgy meat?
Both of which are moral judgements, based on personal beliefs, but I'd imagine they'd get short shrift.
However If someone claims to base their objections on superstitious religious mumbo jumbo more often than not get an automatic get out clause.
Well done NHS Greater Glasgow and Clyde for taking a stand!