Like you said, Maths isnt a requirement for the course you want to apply for so you dont necessarily have to take it on further to A2. If you enjoy spanish more, then you would probably be better to carry it on as you are more likely to do well if you enjoy it, and noone wants to be wasting their time doing subjects they dont enjoy. Consider which subject you are likely to get a better grade in as another factor, as you want to be balancing what you enjoy with what you are good at.