For starters, she lives in Barcelona. Spanish Bachillerato in Catalonia includes a Treball de Recerca (TdR, TR).
It's a research project, a good one about 80 pages long, that takes months to complete. Way harder than the EE (some friends knowing about both think the EE is really, really easy, if you compare it to the TR). The EE accounts for 1 out of the 45 points. The TR is a 10% of the total Bachillerato average mark.
Plus, IB consists of six subjects, whilst Catalan Batxillerat has 10 or 11 (or 12, I'm no longer sure).
Irish unis will probably know better how the IB works than how our Bachillerato works.
Even though the circumstances have not been good, leaving Batx and doing A-levels is one of the best things that has ever happened to me.
If it serves any purpose, I've got a friend that got admitted to do (from scratch) the IB at a UWC, after he had ended 1r de batx. He accepted, and will enter uni one year later just for the sake of doing the IB (true it is at a UWC, but anyway), losing an entire year of work (he retains the knowledge, useful now, but after two years, these marks are no longer valid for anything, I believe, as opposed to AS-levels).