That's one of the reasons most of us here recommend that people stay away from Hyundai/Kia products. (See the site Hyundai/Kia topic for further details.)

There is no manufacturer that across the board that has not experienced oil burning problems, though Hyundai/Kia products are particularly notorious in that regard. You have to research the specific model and engine you are considering before purchase, and if buying used have the vehicle inspected by a good mechanic first.

Every manufacturers made oil burning engine. You need to do research on model, engine, and year on which burns oil excessively.

Even though it is true all manufacturers have had oil burners at some point in the past, nevertheless Toyota and Honda are still your best bets.  Research the model, year, powertrain carefully of course but I’d start with those two brands.

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Also, nothing surprises me about Hyundai Motor Group products.  It’s the reason Scotty and the forum consistently recommend to stay away from Korean automakers.

As others have advised, you would need to research the particular make, model and year vehicle that you are interested in. One good site that provides this and other useful information is:

carcomplaints.com

how often does she change the oil?

The oil and filter is changed every 3000 miles. I send an automatic reminder to her phone weekly to check oil level and make sure she carries 2 quarts of oil in her car.  

Considering that engine holds 5 quarts of oil you're talking 60% of the oil must be replaced between oil changes. That is extremely excessive. The car is six years old. Bring it to a reputable dealer and have it checked. You might be entitled to a new engine or a repair. The problem will only get worse if you do nothing and then you will end up getting stuck somewhere.

Hyundia/Kia have been ordered to replace a bunch of engines as part of class action law suites.