I am not sure the exact deduction but she would not get credit for doing the skill at all, which may be .8 but I am not sure.
She may be better off doing it with a spot which I believe is .5 if the coach actually touches her during the skill. If coach is just on the floor and does not touch her there is not a deduction - if I understand correctly.
I should probably be quiet and let someone who knows for sure answer
No, she would get credit for the RO BHS, but she would get a .3 deduction for stopping between skills. If the coach spots, she would lose .5 for the spot, plus the full value of the element. In other words, spotting would incur a MUCH greater deduction than a stop.
Basically you could look at her floor routine as starting from a 9.7 while the others who have all the skills start at a 10.0. Whether or not its a big deduction depends on how the rest of the routine is done. Bottom line is you never want to give away points---the judges will find enough areas to "ding" on without the gymnast balking or needing help with a skill.