If I understand correctly, the relationship between you and your DNA match Marsha is 3rd cousin once removed. My understanding of the current WikiTree guidance is that since your relationship (being 3C1R) is more distant than 3rd cousin, triangulation between 3 or more distant relatives is required to mark the associated relationships as "confirmed with DNA". See the triangulation help page for more details.
If this were a matching scenario for which you could use one-to-one GEDmatch confirmation (again, I don't believe that it is), I believe that you have provided all the necessary information (and then some!) in your confirmation and associated statements in Midge's profile. The only thing that I can see to recommend at this point is to modify "Relationships are confirmed by a GEDmatch test ..." to reflect "Paternal relationship is confirmed by a GEDmatch test ...", since you would have been marking Midge's relationship to her father (and not to the one to her mother) as "confirmed with DNA", if this really were a one-to-one matching confirmation scenario. That verbiage in the confirmation statement would also avoid a 213 error on the weekly Suggestion Report, if the relationship were marked "confirmed with DNA".
While I don't believe that this particular matching scenario meets the WikiTree criteria for marking the associated relationships as "confirmed with DNA", I believe that the info that you've included in the profile still supports the relationships. So you may just want to leave that info there and change occurrences of the word "confirmed" to "supported" at this point in time.