Is vaseline advisable to put it on my daughter's finger after she did a surgery to separate her stuck fingers ?

That depends on: The stage of healing. It's safest to contact your daughter's surgical team for an answer. I'm guessing it was done at a major medical center & that your daughter was evaluated by a geneticist for causes of syndactyly. If not, it may be worth asking about. With the help of an occupational therapist, many children develop excellent use of the hand & fingers after healing. Best wishes.

No: I would suggest that you use a neosporin ointment to ensure there is no infection. Talk to your surgeon and ask their recommendations.