the fact he isn't already thinking of making her strong too is a faulty point here.
would he really hold back on training her? who cares if she doesn't have experience.
she can learn. but he talking like he will be the only one fighting, and she must be protected is kind of dumb.
train her, from the first day, while things are still slow. and then you can easily give her the reason to stay back, at least until she learn how to defend herself a little bit.