I have bought some special present for my friend's birthday (29th June).
Now I am writing some sentences about the moment when she sees my present
(it has not happened yet, I am imagining).
I think she will be very happy when she sees this present.
I think she will be very happy after she has seen this present.
I want to pick sentence 1, but I think sentence 2 is also correct. I don't know which is the better.