Firstly congratulations to your client and I hope she is making a full recovery from this terrible disease :hug:
mmmmmmmm difficult one and best act on side of caution and get her to check with her doctor before anything
I'm sure all will be fine except for the issue of the tumor removal itself which presumably required surgery
if so then there is a wound to the skin...certainly do not apply a spray tan if the skin is broken,inflamed or that the scab hasn't healed fully
In so far as the outcome of the tan itself is concerned this should be fine given her treatment but advisable to perhaps notify her that there could well be the slight chance that the tan may develop oddly...im confident it should be OK but well worth making this observation
HTH and good luck :hug: