It is not unusual to see some discharge after a spay surgery especially if she was in season. I woukd exoected it to have some color though. Examine her vulva area and see if it is swollen or there is any sign of irritation or inflammation. She could be licking just to keep herself clean or the area is irritated. If she is eating, active, urinating and defacating normally, I am not seeing any red flags. However, I am not a Vet and, since we are nearing the weekend, I would suggest you call the clinic where you had her spay and speak to them about this.
Do come back and update.