@ChimneyPot
That is a very unusual situation. My ex put me through hell in the 10 years it took to get to court. He was unreliable, paid erratically, never (not once in a decade) contributed to medical or educational costs.
If you are prepared to go into the witness box & give evidence (something most judges strongly discourage unless there is a massive gulf in positions), you can bring up such matters.
Otherwise the judge will look at a) each set of affidavits b) the offers from each side c) housing, maintenance, pensions and educational / medical costs. That's it.
In OP's case, as far as the judge will be concerned, her ex has a history of paying regularly. It doesn't matter if it is the mortgage or maintenance, unless the payment is tiny. It's the same difference.
In terms of a forensic accountant, they exist but you'll pay a lot and for what? If her ex hasn't disclosed financial details, the case won't proceed to court anyway. For very HMWA individuals, perhaps.
My ex left gaping holes in his statements (where he got bonuses) and it wasn't taken into account at all.
Ultimately the maintenance I got was outwardly good (and certainly compared to the UK!) but as he never sees them (again, not taken into account, as he said he wanted to but I prevented it, a Section 32 report found in my favour but proposed counselling for him, he agreed so judge said after counselling, he would then see younger DC every second weekend) and won't pay towards medical etc costs (he is ordered to do so; so far hasn't, yes I can take him back to court eventually but it's more money & stress) it's not as good as it looks.
Unless you've directly experienced an analogous situation in the Irish courts be v careful what you advise. I've lived this for a decade now so I am well-used to it. It's a horror show.