She should be feeling movement by now. Tell her to ask her Dr to do an ultrasound. Even with a heartbeat, things can still go wrong. My SIL lost a baby at 30 weeks due to a massive abdominal tumor (the baby had the tumor). She said she never really felt the baby move, she had been pregnant before and thought that this baby was just less active, etc.
There can be reasons for her not to be feeling movement (fetal position, location of the placenta etc) but it is better to be on the safe side and make sure.