Miles & More (Lufthansa, Austrian, Swiss, and other partners) - Can you use UA miles to upgrade UA codeshare on LX metal?

A friend is buying a discounted Y ticket SFO-ATH-SFO for a trip in September.

She has plenty of UA miles but of course there are no awards available now.

She can buy the ticket on LH or the same flight on a UA codeshare. Will there be any chance to upgrade at check in using UA miles? Or will the fact that the original booking is some discounted fare make her ineligible no matter how she books it?

Sorry if this belongs in the UA forum.

A friend is buying a discounted Y ticket SFO-ATH-SFO for a trip in September.

She has plenty of UA miles but of course there are no awards available now.

She can buy the ticket on LH or the same flight on a UA codeshare. Will there be any chance to upgrade at check in using UA miles? Or will the fact that the original booking is some discounted fare make her ineligible no matter how she books it?

Sorry if this belongs in the UA forum.
You are correct. Your friend can only use UA miles to upgrade on LH or LX from Economy to Business if she buys an expensive Y or B booking class ticket. If the original booking is a discounted fare she will not be able to use miles to upgrade no matter how she books it.