Answer first
Women with pattern thinning usually keep their hairline but notice a widening parting and less volume on top, which the Ludwig scale grades from mild (I) to extensive (III). Because female thinning has many possible triggers, a doctor's check for iron, thyroid and hormones is a sensible first step alongside scalp care.
Grade I
A slightly wider parting, noticed mostly under bright light.
Grade II
Clear widening and less volume across the top.
Grade III
Thin coverage over most of the top of the head; toppers often help.
Questions
Is it always genetic?
Not always; iron, thyroid, hormones, stress and illness can all play a part.
What helps most?
Finding the trigger first, then a steady routine and patience.