Yes, I'm not familiar with Zelle but I have used my credit card to pay for something for the host family and they have reimbursed me on Venmo which I put into my bank and then pay my credit card bill (sometimes a purchase is more than I have in my bank). Basically, the money has a trail and can easily be explained if asked. I don't think there is anything to worry about since the yearly pay is under 12,000. If some of this money is in gifts you are legally allowed to gift people money (up to 17,000$ in fact). I don't report to the government when my mom and grandpa give me money for my birthday.... and you guys are her family while she is in the US.