Okay here is a portion on her powers:
Wanda and Pietro discovered that they had peculiar talents. With a particular gesture while she was in a certain frame of mind, Wanda found that she could cause unusual phenomena to occur. When Django began to steal food to feed his starving family, enraged villagers attacked the gypsy camp. Using his phenomenal speed, Pietro fled from the camp with his sister. The traumatic circumstances of the separation from their family were so severe that not until well into adulthood could they remember anything but the barest details of their childhood. The next few years, Wanda and Pietro wandered central Europe, living off the land.
One day, Wanda accidentally caused a house to burst into flames with her uncontrollable hex powers, and was chased by superstitious townspeople. Despite Pietro's attempt to defend her, they were soon overpowered and about to become victims of mob violence when Magneto came to their rescue
Unfortuantely I couldn't find too much
Here's what I found, despite it's not really on topic
Powers and Abilities:
channel natural chaos magicks into the generation of probability distorting hexes
Notes: Scarlet Witch's powers have developed almost constantly over the years. Originally her hex bursts caused disaster and calamity wherever they struck. After some light mystical training with Agatha Harkness, Wanda learned how to focus on probabilities and hone her hexes to specific outcomes. More recently, Wanda has learned that her power is the manipulation of natural magic, which she now can use for self-levitation, limited control of the elements, detection of magic and unnatural phenomenon(like mind control), and focus her power to negate said phenomenon.
What I understand from that is the fact that her presence provokes some kind of modification in the probabilities of a disaster happening...