The DEN-SLC-LAX-ICN segments (all with DL flight numbers, operated by either Delta or Korean) will earn 100% OnePass EQM when booked in an M fare class.

Because the last segment (ICN-SIN) has a Korean flight number, Korean will "map" the Delta M fare code into one of their own fare codes. With a little luck, this might map into a fare code like "S" and your mother will earn 150% OnePass EQM. (I am not sure how to find out the fare class for this segment... I am pretty sure it will show up on the ticket, but I don't know which airline will be able to tell you this with certainty before you buy the ticket. I have had luck using ITA to show this fare code mapping.)