I'll tell you what she is going to say. " A loan? to buy a car? why didn't you take out a loan to pay for the Jeep to get fixed?" And I think she would have a good point. If you can't afford to pay cash for a toy, you should pass on it.
And I'll tell you something else. If you think you are headed towards marriage with "so little" money that your in law has to fix your cars, or loan you money for something that cheap, YOU cannot afford to get married.