If you select the wikiData ID in the suggestion, it brings up Lydia Russell's record on wikidata. Scrolling down has a link to her 'child' Ralph, who is listed as her 'child' in wikitree. Selecting that, you can verify that they are the same person on both sites, therefore, the mother Lydia is correct.
Scrolling down or searching on the wikidata page for Ralph, you will find an entry that has WikiTree person ID Richardson-15054 which matches the WikiTree person ID for her son. The Suggestion is because Lydia's page on wikidata doesn't have her WikiTree profile ID, as Ralph's page has.
Returning to Lydia's wikidata page, scroll down to the Identifiers section, which has The Peerage person ID. Below that, select Add Statement on the right side. In the Property field start entering wikitree. You will see a drop down for WikiTree Person ID, which you can select. Then in the open box, enter her WikiTree Profile ID Russell-14988 and select Publish.
I think that is the steps, but I didn't want to actually do it, so you can try it. Once that is updated, then you can update the Suggestion with Corrected and your comment.
Hope that helps.