[General] Her main job is to....

[Silverobama]

One of my aunt's relatives is working in a factory. The factory produces canned fruits. Every day she needs to add the preserved fruit into many cans. Is it natural to say:

Her main job is to can the fruit every day.

 

[tedmc]

She is only involved in one step of the production/canning process,

Someone who works in a production line is generally called a production operator. I'd say she is a production operator in a fruit cannery.

 

[emsr2d2]

If that's the only thing she does at the factory, it's not her main job but just her job.

 

[Tdol]

How about:

Her job is to can fruit all day.