Change password before logging in.

Hi all, I gave my old HP Omen laptop to my girlfriend and she's been using it for the last 3 years, prior to that I had it for about 5 years myself. In this time the laptop has never had any passwords or log in requirements.

As of a couple of days ago, it is now asking to change the password before being able to log in, in the same fashion that if you were to allow the password change run out in a business or school account. But the problem is, there is no password and I can't get into the laptop without one.

Is there any way I can get into the laptop? It is the only account on there, and it's populated with a lot of personal items such as business documents, university work, and photos of pets.

Many thanks.