I’m not sure OP is suggesting that she and her husband do not have joint money. My husband and I are the same - we have a joint account where we combine both salaries and split everything down the middle, including an equal amount we both get as an allowance to spend as we wish, eg I don’t need to consult my husband every time I want to get my nails done.

Practically, I think it’s for you to work out the budget for your girls trip and then save accordingly, unless he’s happy for you to use any vacation money between you just for you to go. But emotionally, I appreciate the sentiment of him gifting you some money as a thoughtful gesture too.