Think this is the third month - quite late developers are Ragdolls - she's just 1 and hasn't got the really long fur like her big brother and sister yet, although same size as her 2 year old sister now, but much smaller than Simba - he is tall. Her 'siblings' from the same litter have long fur - she still has the rabbit like fur.
Her coat will probably come in this autumn. One, it's been very hot, and two, because she's calling, it does cause girls to lose condition. Once she's been spayed, she won't have to deal with her hormones yo-yoing around all over the place.
A friend breeds Nebelungs (also a semi-longhaired breed), and likewise, they're slow to mature. Her entire girls also have a much sparser coat than her neuter girls, even though they're mostly all on superlorin to prevent any "oops" litters.