please see this link and look at the discussion under "promotional event" and later. There are other blogs about deductibility of wedding expenses but few discuss the situation when one is in the business of wedding planning.
https://bizfluent.com/can-wedding-costs-be-deducted-as-a-business-expense.html
There is no right answer in your situation. if audited facts and circumstances would be taken into account. I also have to agree that since you are not married in 2024 it's not your business (you say it's her business) so you have no deductible expenses. I strongly recommend consulting with a tax pro when doing each of your 1040's for 2024 and also get advice for 2025.
being too aggressive in deducting expenses, COULD result in IRS disallowance.
