If she was spayed before her first heat I wouldn't even bother. It'll likely be more uncomfortable for her than anything else because none of her sexual organs were allowed to develop to maturity. Odds are that she'll signal you to stop immediately. If she was spayed after her second heat there's a slight, and I do mean slight, chance that she may enjoy a little bit of clitoral stimulation. But seeing as she has been robbed of most of her estrogen producing organs, there's a good chance that she'll still reject your sexual advances.