having purchased a ring online a couple years back, it turned out to look very differently when I saw it in person finally.
Aquamarine is a difficult stone to produce photos of that resemble even close to what it would look like in person.
I would highly suggest you Not buy anything online. You have to wear this ring for the rest of your life, see it in person, make sure you love it.
that being said, if you must have this ring, make sure they have a 100% return policy.
that's a lot of money to spend for something online that's quality can vary so much from stone to stone... I would advise against it.
and congrats