@WayOutWestMom hmm yeah I have talked to some friends over at the US and they all seem to give me same advice 
You see I still don’t know which colleges will accept me as an Undergrad, if they are great colleges , I wouldn’t mind studying just as a Bio ( or any other major) major So nothing is decided and nothing is permanent.
Looking at the situation I might just go with Top unis in Ireland and then go for the USA after.
To be honest, your major(s) and the quantity of majors does not matter in the eyes of med schools. If you are doing a biology or chemistry major because you feel as if you ought to choose some combination of those, you should really think about what you really enjoy. If they ask you in an interview “why did you choose your major?”, you want to be able to show that it was because you were passionate about your choice, not that you simply thought it would make you look good. Also for pre-health of any kind, it is wise to have a plan B in mind right from the beginning. If med school didn’t work out, what would you want to do with your life? Use that to select a major.
You could do two majors if that works out for you. Each major has its own set of requirements, and if you do two majors, you need to fulfill both sets. I am sure biology and chemistry majors may have a great deal of overlap, but you need to carefully consider your institution’s policy. It is possible that a policy will not allow you to count a single class towards multiple requirements simultaneously - in other words, you have a choice for which requirement you want a class to fulfill, but you can only choose one. In addition, some institutions also place a restriction on which combinations of double majors is allowed, and they may forbid those where there is too much overlap. If doing a two majors will require you to take additional semesters, then I would advise you to just drop one of them. If and once you get into med school, you still got from point A to point B, thus it is not worth the extra tuition.
A top student is going to med school one way or the other.
As far as OP concerned, as a Foreign Student from Australia, it does not pay to come to the USA just for “trying out” in pre-med, with only 2% overall acceptance rate vs 40% overall attendance rate for US citizens . OP would be much better to become a doctor in Australia and come to the USA if he/she still want to under FMG.
@artloversplus thanks for info
I don’t get " it does not pay to come to the USA just for “trying out” in pre-med".
She means there’s no point in coming to the US just to see if you like premed. However my impression is that what you’re interested in is biology, and a big difference between Australia and the US, especially if you get into a LAC or honors college, is the ability to join a lab as an undergraduate.
Most US med schools (and other health professions schools as well) do have an explicit policy to say that international students will not be considered, end of story. Med schools with such a policy typically cite concerns about those students’ abilities to pay as the main reason. I guess the point @artloversplus is trying to make is that it is not a worthy investment for an international student to come to the US for undergrad simply for hoping to get into a US med school.