Molly is not the most emotionally stable person on the planet. She is obviously still in love with Rick and having a difficult time coping with his death even after ten years. This occasionally results in minor hallucinations (although given the O'Shannon bloodline and Fi's ghostly encounters Molly might not be imagining as much as she thinks she is). She had a turbulent relationship with her parents when she was younger and is still trying to work things out with them. Then there is the stress of trying to raise two children on her own.
She also tries very hard to walk the line between "cool" and "responsible" for Jack and Fiona. She can sometimes seem unusually overprotective, but at times she is also unusually understanding. She is especially concerned that her daughter Fiona seems to be following in Rick's footsteps. She fears that Fi's fascination with the Unexplained could lead to the same fatal consequences that Rick's did. Although she often tries to (emphatically) discourage Fi's delving into the other Realm, she also seems to realize that Fiona's "extreme possibilities" are possibilities nonetheless. Ironically, despite her aversion to the Unexplained, there are the occasional hints that Molly herself has a bit of the "Sight" - minor clairvoyance.