A loan is essentially a contract; by that, I mean that it is subject to whatever terms were agreed to when the loan was made, and this applies equally to loans memorandized by a written agreement and to loans per an oral or verbal agreement. So whatever were the payment terms when the money was loaned to you, that's how/when you must repay, and your friend cannot change those terms unilterally unless the loan agreement itself gave her the right to call the loan due earlier at some point. If you have not been paying as per the loan's terms or agreement, then you would be in default (even if you've been paying what you can), which may (again, you have reference the agreement made at the time) give your friend the right to call the full balance due.If there were no explicit payment terms, then if you look at how you've been paying for the past 3 years and how your friend has been accepting payment, that history or practice could be used to establish what the mutually agreed-upon terms in fact are.