My son goes to the Morgan Autism Center in San Jose. I think they have HS students help out with an after school program (my son isn't part of that). Have her call them and ask 241 - 8161. They are located near Valley Fair mall.
HS students help out with the Challenger baseball in the spring and VIP soccer in the fall. That is usually on Sundays. Send me a message, and I can get you in touch with the organizers if that interests her. These teams usually have youth with a wide variety of disabilities.
HS students also help out with Special Olympics -- my son does the basketball. I think the first session for him is this Sunday 9 - 11 at Cupertino HS (Finch Road). I don't know what you need to do to sign up as a volunteer. 392 - 0170. They also play in Santa Clara on t and th evenings.
She could check with Parents Helping Parents in San Jose for more volunteer ideas. php.com