$3,000 is no small amount of money, do people really feel so much shame in giving someone plain old money that they have to buy a gift card?
A gift card is almost like buying a stock, except it's much more risky and gives you zero benefits compared to the cash that paid for it. If you want someone to be able to travel for $3,000 just give them $3,000.
Voluntarily spending £3k on a gift card seems utterly insane. I imagine a lot of people would feel quite confused or upset about that considering what they could also spend a few grand on.
Money is the other extreme, it says "I really have no idea what kind of gift you'd like", so apparently you hardly know each other.
Gift cards are at least a small step up, you show you think the other likes to travel.
I should give her a call.
On the one hand, giving a well-received physical gift shows that you know the person enough to get them something they wanted. On the other hand, it also risks they'll have an unplanned item that kind-of-but-not-quite matches what they actually wanted, creating friction and inconvenience in their lives. I know this is a custom, but personally, I'd much prefer to get a monetary equivalent instead.
(One custom in my area I know where giving actual money is still expected is weddings. This is usually justified by the fact that organizing a wedding costs a ton of money, so this helps the newlyweds recoup the expense.)
If you used a credit card, you get your money back in the case of bankruptcy. If you used cash you may not unless you bought bankruptcy insurance.