An Infected Lady is one of the different variants of Zombies. The cause of death of this young lady is unknown, although it was probably not long ago since the body is not very decomposed.
One headshot with a 100% condition Pistol is enough to kill it. This zombie is a bit easier to kill with headshots since she doesn't wave her head too much when walking towards the player. Using melee against this zombie with a good quality weapon is effective mostly if hit in the head.
During night, the running behaviour is standard as all other zombies. If distance or sheer zombie numbers aren't a concern, scoring a headshot when it's running headfirst towards you can be slightly easier.