You can not buy private insurance in the US, that will pay for a pre existing condition. So if she already has cataracts and teeth issues, it not going to pay for them.

There are a few policies for dental, that have limited payment for the first year and then better the second year.

What you want just does not exist, the reason, people would not buy insurance till they needed to go to doctor, buy it, and get treatment, then drop it afterwards.

If you are in another country other than US they may have something.

There are some group policies, so perhaps she can get a job where they furnish insurance at work, that may cover.