The product was designed for those who struggle elevating from and declining to seated position because of special limitations of age, injury or complications like arthritis, etc. If she was on the floor it "may" be possible for her to reach it to help her get up if she has not injured herself or if she does not have physical/health limitations. The bar optimally should be mounted 40"-41" from the back wall of the toilet to the 1st mounting post and 28" off the floor. However, the distance from the back wall can fluctuate a little depending on the size of the person and arm length.
The bar is designed to move slightly so if hit with force not to break. just adjust it as it is within the specified design
If you mean like the fatty roll of Charmin yes - not sure about a "double" roll
You can mount this to a 1/2" or thicker drywall material as well as tile and cement board over drywall of course. 2 LiveSafe anchors come FREE in every box for Hollow Wall Mounting when you cannot hit a stud along with stud mount Hardware for when you can. Moen does not include anchors free with their product which is a $22.00 add on if you need two anchors for Moen product. Also, Moen bar is only 1" so is considered an "assist bar" which only holds up to 300 lbs. Grabcessories holds 500 lbs as long as the wall will support the load. Drywall itself will NOT support more than 250-325 lbs depending on the thickness of the drywall no matter which product you mount. The "LiveSafe Anchors" are actually much better than the Moen Secure Mount anchors because the patented elastomeric band on the back of the anchor which snaps it back to the walls keep it from falling down the wall. It's also easier and quicker to install. It can also be taken out and re-used. Also, if you hit a cross brace at the top, all you need to do is turn the anchor 180 degrees downward and you can still mount your grab bar. See this install video for visual details https://youtu.be/8bmSfaHf8DA