While a teacher, this person did not directly instruct you in a professional, academic environment, and for this reason, I would not get a LoR if I had absolutely no other option.
I agree.
This individual will be able to vouch for your abilities as a tutor, perhaps, but will not be able to recommend to a Pharmacy school AdCom that you're capable of excelling in a rigorous academic atmosphere, which is (mostly) what they're looking for.
If you check out the AACP website, it has a listing of each CoP and what type of LoRs they require/accept. I could link it for you if the AACP website was functioning properly at the moment but alas it seems to be having some connection problems!
This person is also a poor reference. If you're really out of options, then answer these questions:
When you tutored for her cousins, were you paid? If so, did you tutor other students in a similar situation at any point? If you can answer yes to both questions, you could use the math teacher as a former employer. It's still a weak LOR, and only a last resort, but there's an angle you could exploit if you need to. Still, I'd get a chem prof if you there's any way you can get a favorable letter from one. O Chem would be better.