When they invade your space walk off, at an angle, through your side. Puts them at a disadvantage in pursuit, puts quick distance between you and the aggressor and places more people between the aggressor and the target.
Whew. ..but yes, good points to remember and follow.
Additionally, if you can’t avoid the situation from becoming physical I recommend the following (from personal experience and self-defense classes I’ve taught):
Grab the hair of the nearest group member (that pony tail would have made a great handle!) and do as much physical damage to him/her as you can. Break fingers, scratch the face, press your thumb into their eye, bite the ear. If possible, run as fast and as far as you can while holding the hair.
If you have already been put to the ground, grab the nearest foot and twist it as far around as you can and try to wrap yourself around the rest of that person so that the others will need to aim their blows carefully.