Clubman, I would strongly recommend you be aware of the following. A P45 (or to give it it's full title, a Certificate of Termination of Employment) is a very important document that has legal effect.
If your wife accepts this P45, she is accepting that her employment is terminated. Furthermore, by accepting her P45, this may have implications for subsequent claims of unfair dismissal. That is, an Employment Appeals Tribunal may view her acceptance of the P45 as accepting that her employment has been terminated. Of course, this becomes extremely important in the context of claims for unfair dismissal or constructive dismissal.
Furthermore, accepting a P45 will also have implications for her claim on maternity benefit. Not only must an employee have sufficient PRSI contributions, but they must be on leave from employment in order to claim. In other words, they have to actually have a job in order to claim - it isn't just sufficient to have enough PRSI contributions.
It's easy enough to check whether she has sufficient contributions, just contact Maternity Benefit Section at Dept. Social & Family Affairs and remember to have her PPPS Number to hand - they can tell you over the telephone if she has sufficient contributions.
With regard to her job however - it is obviously illegal for an employer to terminate the employment of someone on the basis that they are going to avail of maternity leave from work. But is this the case - are they terminating her employment because she's taking maternity leave, or is the employer under the impression she is leaving of her own volition? In addition - it was unclear from your initial message whether your wife is an actual employee of this barber shop - or whether she is technically self-employed and is working there.
I think you both need to sit down with someone who can go through your options and advise you on what you need to do next. (I don't mean seeking legal advice - just advice on your rights and entitlements). If you e-mail me privately - I'll see if I can put you in touch with one of my contacts.