You are correct that it can still lead to rejection, as the requirement was to obtain a grade A (or higher) in each of your three A levels. If you obtain a B in one of them, then you will not have meet the conditions of your offer.
Unfortunately, nobody can tell you how likely you are to be accepted, as it will depend on how all the offer students holding offers for that same course do. Loughborough will have made more offers than they have places, as that know (from experience) that not all offer-holders meet their offer conditions. So they'll first accept all their firm applicants who have met their conditions. They they accept all their insurance applicants who have met their conditions (but have not been accepted by their firm choice). Then they'll see how many places they have left on the course. If the course is full at this point, then you won't be accepted.
However, if there is still space, they'll likely look at their "near miss" candidates (which you would be in this scenario) and make a judgement as to which of these candidates they should accept. In making this decision, they look at your overall grade profile (with your theoretical A* giving you an edge), the subjects in which you have achieved each grade and their relevance to the course (with Biology not being particularly relevant to an Economics degree; is there any chance that your A* would be in Economics?). If that doesn't narrow-down the field sufficiently, they may also refer back to your original application (your GCSE grades, your personal statement, your school reference, etc.) in order to make this decision.
They may also opt to open the course to Clearing, in the hope of getting AAA (or better) candidates that way. (Students can "upgrade" their university via Clearing if they did better than predicted; there will also some students for which an achieved AAA didn't meet their firm or insurance conditions.)
For all of the above reasons, the answer to your question is unknowable, unfortunately. You will just need to wait until A level results day.
Good luck.
