Given the current situation within the EU, I would doubt that Croatia's entry into the EU will have any impact on the visa situation for several years to come... so I doubt that it will be of much use to you.
As for gaining a work permit on her own merit, again I would not hold out much hope on this front. In addition to everything else the employer must show that there is no EU or EA (e.g. Switzerland) person available to take up the position, this is usually done by advertising the job locally and abroad. However from some areas (Clerical/Admin/Finance/Banking being one) this is not enough as it is clearly recognized that there are more than sufficient applicants available within the EU to fill such positions. So unless your girlfriend has a PhD in economics and has a national or international reputation in this area, it is going to be a very hard sell.
I would expect your best chance is marriage or some kind of registered partnership agreement that would allow you to apply for a visa under the heading of family reunification.
One thing I would advise is to make sure that you do everything by the book, as any restrictions issued by the Irish authorities are EU/EA applicable. So the penalties can be very restricting!