Just my opinion, but for a new shooter, a thumb safety might be a good thing. Start from the beginning to learn the safety feature, and as you practice with the gun, practice with the safety. Practice both putting the safety "on" and "off". Just as we want "point and shoot" to become ingrained, so can we ingrain "dropping" the safety. It won't interfere if later she chooses to carry it with the safety off, at least not like it would if she had never practiced with a thumb safety. If later on she changes weapons, she is prepared for either.