@edgarblythe,
Maybe she chose a bronze plan, which has cheaper premium, but a higher deductible.
For the heck of it, I just went onto healthcare.gov and entered the following info, trying to imitate your sister.
I estimated I was 60 and made $30K a year.
The bronze plans that came up all had $5000 to $6500 deductibles.
The silver plans had a high range of deductibles, and the lowest premium was $182/month
The gold plans had low deductibles, but premiums of $280 to $800 dollars.
You can go on there and enter her zip code, age and approx income and see what comes up.