it will only go up. She bought at $4200

How soon can we REALISTICALLY see $4200 again and upwards?
What an evil grandson to told his grandma to risk all her lifesavings only in a type of investment (bitcoin). There's nothing wrong with investing bitcoin but just don't put all of money in it. But you're lucky that the price now is above your grandma's buy price. Your grandma can still get more than 50% of profits if she sold all of her bitcoin now. (Regardless whether your story is real or not)