Yes Art Foundation could be a good direction to go in - there is also the Access to HE Art & Design diploma; that is accepted at some universities in lieu of an art qualification. Your other option is to ensure she develops strong art skills / animation skills herself and apply to the universities she is interested in. Depending on how much they need students, an art qualification may or may not be important.
The amount of free teaching in animation/traditional drawing on Youtube is staggering; look at the Proko channel, or look at ctrlpaint.com or search for the software she is interested in on Youtube (you haven't said what type of animation she is interested in). A copy of Richard Williams' Animators Survival Kit will show her the basics of character movement. If you can get her some private life drawing classes (as long as they are taught by someone who can draw properly) that will really help.
It would be worth getting in touch with the admissions tutor for each course she likes the look of and showing them her portfolio. I know I get 3 -4 applicants every year who lack art qualifications but are incredibly talented, so I find ways of getting them in - but I will say the majority of applicants without an art qualification do not have the art skills we need in a student - so we tend to reject anyone without the correct qualifications, but will review their work if they appeal. So I would say try to apply at the same time as other A-level students and see what happens - if you get nowhere then she should do an additional art qualification and try again afterwards, but you might get lucky and not need that stage. Talk to the admissions tutors for those degrees and see what they say; every university / course has different requirements.