This is a step that adds about 12 inches of height in a kind of ladder.

The first step is inside the cabinet door, I would add some teak or plywood to the inside of this filler face to give it more strength.

Then to the right, I would add this 6 inch step that I mocked up in cardboard.

The idea for the added step is to use a long hinge at the back of it, tying it to the face of the filler, then add a barrel bolt (or slide bolt) to the back of it to ensure that it remains in place when it is being used. The step would also rest on the lip of the door face frame, which I will strengthen with teak or plywood on the inside.

The hinge and bolt would allow the step to be moved out of the way for access to the interior of this "cabinet." It is more of a convenient catch all.

Below I show the mock up of the step. The hinge would be on the back of the right side of the cardboard as would the slide bolt. The step would be 5 3/4 inches wide. I plan on step depth of 1 1/4 inches... so somewhat as shown.

To get out of the v berth, she can just slide out... it is the getting in that is an issue.

Yes, there is a drawer in the back of that cabinet. (two actually, but I can only use the top drawer by removing the filler and lifting the v berth cushion. So it is only used for items used very infrequently.