Nothing is running yet, and nothing is being charged.
If you signed up first as a family member, there is no countdown while you get things ready on your own. Your fourteen days begin the day your loved one joins, and you both get the full fourteen together.
Why it works this way
Because the alternative would punish the most common thing families actually do.
Adult children look first. They set things up, read a little, work out whether this is worth raising at all, and only then have the conversation with a parent. That conversation is not something to rush because a trial is burning down.
So the clock waits for the person the whole thing is about.
What you can do while you wait
Quite a lot, and none of it costs anything. Look around, read the Family Hub guides, work out what you would actually want shared, and get a feel for what you are asking her to join.
There is no deadline on that, and no nagging.
If she signed up first
Then the clock started the day she created her account, and it runs from there. If you joined a few days later, you are joining a trial already underway rather than starting a new one.
And when the fourteen days do end
The account moves to the Free plan, which never expires. Nothing is deleted and nothing is charged. Upgrading is a decision you can make later, or not at all.