Sub account transfer?

I couldn't figure out how to add my older sister (we are 22 and 24) to my playstation without making her my 13-year-old daughter. So now she's technically a minor with a child account. Did i mess up? Was there an easier way to do that?

She is planning on one day getting her own ps4. When she does that, will she be able to easily transfer from being a sub account on mine, to a master on hers? How would she go about doing that?

Thanks in advance.