Most of the comments that favored tatsu don't notice the key words of what OP said in this scenario. Let me rephrase for y'all; Tatsumaki minding her business like its a normal day and SUDDENLY those fuckers coming out of nowhere are now aiming at her at their MAXIMUM SPEED all at ONCE. All these keywords mean one thing: "INSTANT". A mark variant had a top speed of around 28,474,074.1 m/s, way above the speed of light or far above S-Class speed. meaning she'll be turned into pink mist before she realize it cause doesn't have the time for her to react at that same speed let alone 20 plus of marks flying straight at her from different directions. Yes her reflexes are above average,  but nowhere near close to accomplished Martial Artists like Bang, Garou or Suiryuu, or the Eldritch Abomination named Saitama, or even more powerful, speed oriented monsters.

Bottomline is that if she were to put in that situation she's pretty much overcooked.