I use Speer 124 grain Gold Dot Hollow Point. It feeds through all of my 9mm firearms including my SUB 2000. I saw independent testing showing excellent performance for expansion and penetration to FBI standards and when fired from the longer barrel of the SUB 2000 the bullet was still accelerating. Testing showed that this round would accelerate up to a 17 inch and lost velocity from an 18 inch barrel. I have carried Hornaday Critical Defense and Federal HydraShock and they also perform within standards I have except for in the carbine. All would trust all three of those rounds in my firearms. I just like knowing that whatever 9mm I pickup and whatever magazine I grab, I know I have the best ammo performance for my equipment.
I have never used the safety slugs, and I personally feel that it is kinda like "snake oil", has a great sales pitch, but in the end will it do what it advertises. Will it give adequate penetration to stop the attacker. If you get a good hit could the round begin to pulverize before hitting a vital organ allowing the attacker to continue. With a quality hollow point the round would expand damaging the tissue in the attacker and slowing the round while inside the target. The quality hollow point, in my opinion, give you the much better chance of stopping the attack and while I don't mix ammo in my magazines, maybe she could load the magazine with a quality hollow point and load the top round and chambered round safety slugs. That way for the first two rounds doesn't stop the attack rather that just shooting more, for the situation, ineffective ammunition she has a more effective round that she could use. I still think that just using hollowpoints is the better way to go.
Just my 2¢.
