It’s because you’re female. Contractors are notoriously dishonest and sexist. For future reference:

-Always work from the assumption they are trying to rip you off until they prove otherwise.
-Get everything in writing.
-If possible, buy the materials yourself.
-If they want money upfront give them no more than half down, with the other half due on completion. Or negotiate pay-as-they-go, especially for longer projects.

They’re a business. As such they should have credit, etc. So if they cry poor at your refusal to pay upfront, look them in the eye and coldly remind them that their finances aren’t you’re problem.

The most effective thing I’ve ever said to a f-up contractor was “you’re fired.” Suddenly the contracted-for thing he “didn’t need to do” magically got done. But that won’t work if you pay them everything front.