I advise all clients not to use Dove. It is a nightmare for spray tanners. If used before the tan it creates a barrier on the skin and the tan doesn't take properly, probably due to the moisturisers in the product. If used after a tan it seems to strip it quicker, possibly due to its Ph level.
I always ask if they have used Dove in the consultation now and also ask them if their skin is product free. If you have advised the client to prep properly and not to use dove and they do then you can't be accountable for the tans outcome. You will sometimes get product remnants on the skin that go green but generally the tan will be fine once washed off. If client did wash off I would charge for a respray. It sounds harsh, honestly I'm very reasonable but you can't afford to spray for free when client has not taken you advise x