Parental seperation

Hey guys. So my parents are going through a rough patch. If you asked me 5 years ago if they would ever have troubles i would of said no way. They wrre solid. Crazy for eachother. But my father got a female collegue. At first everything was fine. My mother works in my dads department at work so she usually made lunch and they ate together etc but he suddenly stopped and started spending all of his time with this woman. Mum kept saying she wasnt comfortable etc. But he just shoved her off. There was no understanding on his behalf. Now hes been acting heartless to her and acting suss as. I think hes cheating now ive seen it all. Mums just moved out. Im so shocked. Has anyone got advise on dealing with their parents separation? What happened long term? I never ever seen this day coming. That bitch better not start dating my dad 😭 im so destroyed by this.