Teen on the one hand those 3 A levels are a tough combination with a7 at GCSE, especially the further maths. (Unless there is some mitigating circumstance such as she was expected to do better but was ill on the day of the exam).
On the other hand, someone at the college signed off the A level choices, so they must have thought your DD is up to that combination.
The problem with those subjects is that the knowledge builds. The skills that have been taught in this first term will be required for the topics to come.
I think I'd be looking for a chat with the person who signed off your DDs A level choices ( her teachers or the head of year?) and ask what their grade expectations are and what they think your DD needs in order to achieve those grades as something is obviously not working and there needs to be a plan to get things back on track.