First of all you need to get the whole thing in writting with your friend. Spell out every detail.
From that point it's none of the bank's business why the money is being spent. It's her money. There are really only two times when a bank will question large transactions - #1 a large deposit of cash (over $10,000) because you have to provide an explanation of how you got the moeny and #2 might be a situation like this, but, they would contact her and just make sure all is kosher. The reason they do this is not for legal reasons, but rather they do this primarily with elderly folks just to make sure they aren't getting scammed somehow. All she has to do is tell her bank she's loaning money to a friend in need and that is the end of it. However most banks don't even call in the first place.
The best thing to do is for her to pay the bills directly rather than give you the money. That way you don't show a large deposit and trip the IRS's curriosity. There's nothing they could do since it's a loan. They can't tax that as income. But, it's less headache to avoid them in the first place.
SOOOO - let's just sum this up:
#1 - What is the best way to approach this? Should she write a check for each of the credit card companies?
Have an agreement and promisary note in writting ahead of time with your freind, and have her send the money directly to the credit card companies.
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#2 - What are the negative effects for the friend who is loaning the money?
Stick to your agreement and don't screw your friend, and there won't be any.
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#3 - Is this legal? Will the banks start asking questions about how she is using her money?
As stated they can call and question her just to make sure all is OK with her, but there are no legal questions for them to ask. She can spend her moeny any way she wants.
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#4 - I don't want her to get taxed on anything...so will the banks snoop around if she is writing checks to pay off my credit cards?
No. If your agreement with her is to pay her back, then it's a loan. Neither of you will get taxed.
Keep in mind too, when the check clears her bank, they have no real way to know that it's her credit card acount or not. They don't verify who it's being written to. All they do is verify the signature, but even then it's only if the check is over a certain amount (the amount is different for each bank but usually about $500 to $1000).