What to do about drunken parent (LRS)

Hello and thanks in advance for your help. I’m in the process of buying a house. I’m currently under contract. My mother generously gave me a big chunk of the down payment which she sent to me a few weeks ago. Ever since then, she’s been on a bender and won’t send the accompanying documentation, i.e. signed gift letter, bank statements, etc. The loan will fall through if she doesn’t do this. I’m very confused about how to think about this situation considering how I want to react: get on a plane and go 4500 miles to smack her hard in the face (not really, but I have been fantasisizing 🙂 OR apply my self coaching skills acquired over the last 8 months and, what?, let the house go? Interestingly, she pulled this same stunt the last time I bought a house in 2009. (Although she did come thru at that very last minute.) Our relationship is very strained and I’m considering never speaking to her again if the deal falls thru because of her shenanigans. Please advise. I’m at a loss.