Is there anything special out there to buy that allows someone to move someone on a lift chair?

I would have an OT come to evaluate and advise. The chair may be too big for her.

Would a gait belt be useful in repositioning her?

I guess she has two problems. The first is she has short legs and when she sits on chairs she sits on the very edge. She has a roho cushion which she loves and it does indeed stop most of her sliding. The second problem I have is she slides and slouches down in the chair. I usually solve it with pillows and a geri chair cushion that I put on the bottom of her lift chair at night (she insists on sleeping in her chair stating she can get up easier in it which is quite true as it's a lift chair but the cushion makes it so she can't slide out of the bottom of the chair quite as easily.)

I guess what I'm looking for is something that will let me boost her in the chair yet not result in her sliding out of it. I'm afraid that by putting a sheet or something under which will help me boost her, that it will also allow her to wiggle and slouch and slide right out of the chair as it will be easy for her to move since it was helping me move her as well.

There is a cushion that you can use. I know it as a "wedge cushion". It is thicker on one edge. You place the cushion with the thicker edge to the front of the chair. This keeps the person from sliding forward. It works well unless the cushion itself slides.

So, Roho is the brand name of the type of cushion that my mom uses. I think i would talk to the doctor about this and perhaps have her/him script a PT and or ot evaluation at home to evaluate your lo's seating options.

Is the problem that she's sliding down? Would you still need to move her if she weren't sliding?

The pt at my mom's nh recommended a special cushion for her wheelchair. I'll see if I can find the name of it. I want to it is called a Roho, but let me check.