Wow. First, serious props to you for taking them out of the situation and doing what you can to help. From those pics, it's quite obvious they need some TLC from someone who cares enough to do what's best for the animals... As for how to handle the situation, it's a sticky one. If this person truly is a good friend, I would continue offering money for the snakes while not so subtly implying that the snakes were MUCH smaller than they should be at that size. I would also keep track of the expenses for feeding and caring for the snakes in the time you have them. Maybe during your cash offer attempts, you can pull out the records and say THIS is how much I have spent on food. THIS is how much I spent getting the appropriate housing for them. Maybe then your friend will understand that the the money you're putting into caring for them will likely be around what you're offering to pay for them and logic will prevail. Or maybe your friend will lose interest while you have the snakes and she'll just tell you to keep them, or finally take you up on an offer. Without knowing the situation firsthand and without knowing your friend personally, it's a tough call. I'm leery of business dealings with friends as those are the ones that tend to go bad, feelings get hurt and friendships get damaged.
To sum up my long winded post, good luck in however you handle it. It's not an easy spot to be in... But don't give up and keep fighting for what's best for the animals overall.