Glenn, not everything we say is going to be profound. I've had my share of H2H combat training and I agree that it was valuable. I also know that some people let it go to their head. At least my instructor was wise enough to make sure that I had a reasonable level of humility to go along with any skills I may have learned.
The OP's sister will certainly be better off with training than not but it's folly to plan to take a gun away from an armed assailant. In all the training I got, that was considered a very high-risk, last resort.
At least the training will be useful for unarmed combat and she might even start considering a less-than-lethal defensive weapon.
To a much greater extent than most mechanical devices, firearms are terribly unforgiving of any overconfidence, complacency or negligence.