My reply to her is this:
It is generally not advisable to take out a loan to purchase Bitcoin or any other cryptocurrency. Cryptocurrency markets are highly volatile and the value of a particular coin can fluctuate greatly in a short period of time. This means that the value of the coin you purchase with a loan could drop, making it difficult to repay the loan. It is important to do your own research and make sure you understand the risks before investing in any financial product, including Bitcoin.
What is your advice?
You're correct.
Loan interest is fixed, while Bitcoin price is not. So it is really not advisable to take a loan for your friend to invest in Bitcoin since the price is very unpredictable. Even if he's going to use it for trading, I don't see it a very good idea unless he has enough experience that can back up his decision which makes him confident that he can make a lot of profits out of it so that he won't have sny problem paying up his loan.