Definitely make sure the needle will be directly in front of where she is sitting. I think it is very helpful to have maybe 6 to 9 inches of table space on the right. A lot depends on whether she is right or left handed! I am left handed and I like drawers on the left side.
You can buy lift mechanisms online if you really want to lower the machine out of sight. Otherwise why not make a nice top just to sit on top of it like the older machine cabinets have.