Jack is a person with autism. He has severe intellectual disabilities but he can play many classical piano compositions by ear. Jack probably has a condition known as .

savant syndrome

Explanation:

Based on the information provided within the question it can be said that in this scenario Jack probably has a condition known as savant syndrome. This is a condition in which the individual with a significant mental disability is able to perform certain abilities at a far higher level than the average individual, usually in regards to memory. Such as is the case with Jack.

just be there for her.

explanation:

not necessarily literally but figuratively. also don't say things like "i understand how you feel", because even though you are trying to , you clearly don't understand how she feels (i'm gonna go out on a limb here and assume you've never had a heart attack). also just let her rest. that is one of the best things for you to do.