Fishlock, who has said this will be her last year playing club football, will be on duty with Reign when Wales go to Albania on Friday, 9 October and then again in the return leg in Llanelli four days later.
Should Wales overcome a side who are 36 places in the Fifa rankings – and one they beat twice in the group phase of World Cup qualifying – they will play either Norway or Romania in a two-legged play-off final in December.
Wilkinson has revealed that another recently retired former player, Kayleigh Barton, will be part of her staff for the Albania ties and then Fishlock will have a role should Wales reach the final.
Fishlock previously worked as a technical assistant for Wales’ opening game of this qualifying campaign, against the Czech Republic in March.
Wilkinson explained that Fishlock had been in touch before she named her semi-final squad on Tuesday, adding: “I didn’t appreciate her saying ‘call me up coach, I’m ready’, which I thought was mean, but [she was] a wonderful player and a great leader for us.
“If we are able to get past Albania, she’ll be coming in as a coach for us for the next round.”