Car Loans For No Credit

Is it detrimental to my credit when buying a home to have a car loan on my credit?
I’m asking for my GF. She has no car loans, just active credit cards with zero balance, a 744 credit score. She wants to know if she retains a car loan, and then goes to get a home in 3 months will this negativly affect her score? Or just her income to debt ratio? Advice?
I work for one of the largest (and still standing might I add) mortgage banks in the country. We give people home loans with no credit score and no social security number (foreign national). It’s easier to buy a 500K home than a get 15K car loan if you DON’T have credit. Homes don’t go anywhere. Cars can hide in your neighbors garage, Canada, Mexico, etc when the repo man comes looking…
With a 744 score you will qualify for the best programs out there. If you take out a car loan it might decrease your score.