Can I tell a related story? I don't suppose it helps (but do think you should be OK as you know her address).
I bought something on Ebay and asked if I could collect instead of paying postage. It was something quite expensive (4 firgures). The seller said that they would prefer not cash, and obviously I was reluctant to transfer money without the item. I can't remember why we didn't use PayPal but there must have been a reason!
Anyway, we came up with the following cunning plan. I would go to the house with my laptop and transfer the money in front of the seller. When it arrived in his account, I would leave the house with the item.
All sounds good, yeah? (Well, apart from the risk of going to a total stranger's house, of course, but that bit was fine). So here is what happened.
Money transferred, but did not arrive. I phoned my bank. Standard security checks. Yes, the money had definitely left my account, they said, but might take 2 hours to arrive. Cups of tea ensued.
2 hours later - yes, the money has DEFINITELY left your account but night take TWO DAYS to arrive. Which left us in a slight quandary. At the point the (totally lovely) seller suggested that I ask the bank (who were on speakerphone) whether the transaction could be reversed. They said it definitely could NOT, and the money would arrive in the seller's account. On this basis the seller allowed me to leave the house with the item.
Fast forward another 2-3 hours and I received a phone call from my bank, which went as follows:
Bank - have you been trying to transfer £xxxx from your account?
Me - yes, of course. I've been through security 3 times already. Does the seller have his money yet?
Bank - oh no, we haven't actually actioned this yet as we needed to speak to you first for security reasons.
Me - DESPITE the fact you told me that this transaction had already been made and could not be reversed?
Bank - oh no, it hasn't been.
Me - please action this bloody transfer immediately. I will be making a complaint.
TL:DR Banks are shit.