DD17 is considering applying to U of Edinburgh for chemistry. In their general requirements for US students they list the general scores needed (3 APs of 4 or more or SAT2s with 650) and say certain programs may require more or specific subjects please contact them with questions . So she did. And they sent her a link to the same page.
Welcome to the world of British higher education!
@TomSrOfBoston has a good overall point: the UK unis are not used to a lot of direct interaction. However, the websites really do have a lot of what you are looking for- though Edinburgh’s isn’t the easiest one of the bunch to navigate!
If she is looking at the BSc in Chemistry (and she should read the course descriptions carefully [url=<a href=“http://www.ed.ac.uk/studying/undergraduate/degrees/index.php?action=subject&code=3%5Dhere%5B/url”>http://www.ed.ac.uk/studying/undergraduate/degrees/index.php?action=subject&code=3]here[/url] before choosing exactly which course: Edinburgh is proud of how flexible they are, and they are by UK standards, but not by US standards), you will see that for chemistry they want AAA at A-level, to include specifically Chemistry and Math.
Edinburgh will accept a 4 in an AP or a 650 in an SAT subject test or a 5 at HL IB as an A at A-level (which, btw, is a gift). So there are several paths to meeting the requirements, but all of them require scores in Math and Chemistry.
What level of Math isn’t specified, but the application will be stronger with Calc (and she will be better prepared for the math required for actually doing the work once on the course, as most of her peers will have had some calculus). Although not specified, typically the third score would also be a STEM subject.
Hope that helps 
Look up what subjects are required for A-level applicants for Chem. I imagine Chem, Calc and another science for General Chem
http://www.ed.ac.uk/studying/undergraduate/degrees/index.php?action=programme&code=F104
Math is the one we were looking for specifics on because she is taking the SAT 2 in Math 2, and IB Math SL, but not any AP tests in math so it was not clear if she could mix and match IB Math SL with APs and SAT2’s for the other subjects. She has all other required scores.
My daughter applied with SAT2 result in required subject and pending AP exam in the same subject (Bio). She got an unconditional offer based on SAT2 alone (and a bunch of other scores in different subjects).
With a 6 at SL, probably.
One thing to keep in mind is that it’s not just about getting in: where a subject is specified, having a solid base will genuinely make a difference once she starts as a student. There is a required math class that all first year chemists take, and there won’t be a lower level math class for people who have less math background than the standard A level (indeed, even with a strong background she is likely to find differences, b/c the US & UK math teaching patterns don’t align completely).
Yes. Math instruction in the US is, IMO, behind the times. Even if a kid takes all the calc, stats, physics, and CS AP classes at the highest level, they’re still not going to get to everything covered in A-Level Maths and Higher Maths.
She has taken A1, Geometry, A2, Pre-calc, and SL math. She decided to apply for chemistry after choosing her HL and SL classes and starting the IB program so switching to HL math was not possible. If she gets the 6 on SL math, which we will know tomorrow, I will encourage her to apply and give her some study topics for senior year to bridge the gap. If she doesn’t get the 6 on math, she may need ot adjust her applications.
(I personally was a math minor/chem major so am familiar with math background required in general for chem)