answering facetime call

I have a question on the different ways to answer a facetime call.

My mother is turning 87 this year. We bought here an iPad two years ago, and believe it or not, at the age of 85 she learned the basics on how to use it (with no computer experience whatsoever, really proud of her). We use Facetime, but the way to answer the call is different depending on the 'state' of the iPad. When the iPad is locked, to answer a call you simply slide the slider to the right. This slider is obvious, my mothers eyes are getting worse, but up until know she knows how to do this. The thing is, when the iPad is not locked (she is using it or has recently used it) there is a popup at the top of the screen with an red x or green video button, and when 'clicking' the green video button you get another screen that shows a decline or accept button which you have to click. So two actions instead of one (why oh why?), and also with less clear buttons.

Is there a way to make the way to answer of a Facetime call the same no matter what state the iPad is in (preferanle the once action with the slider)? This is too confusing for my mother.