Let me help:
1. Headgear (facecage optional)
2. Gloves (from MMA to Pillows/Boxing if you like)
3. Mouthguard
4. Cup
Problem is what you have written: "Without getting injured." What do you consider 'getting injured' to be? Because if bruises, bust up lips, bleeding noses and seeing stars consists of 'getting injured,' martial arts is the wrong venture.
Hell, even the crappy (TIC) 'sport-based' martial arts like BJJ that have taken teh deadly strikes taken out have injuries such as sprains and strains all the time.
Knitting (*maybe) might be the only thing that has a low injury rate.
And lastly, about your "beginner, maybe female, who has very soft muscles, tendons and bones." None of those attributes have anything to do with fighting and/or self-defense. If we take Wing Chun, for example, it has a curriculum to build someone up from the ground up. So after the drills and Chi Sau, comes the Goh Sau and then the sparring.
Looking at a boxing gym, first you start with the cardio needed to perform the task, then you're introduced to punching the heavy bag, then you work the pads with a trainer, then you work with a partner - nice and light - feeding each other shots, going back and forth, etc...then you get in the ring and spar and spar and spar. Same thing...from the ground up.
Best,
CTK