Am I just being jealous?

So we are having a grown up slip n slide party later and my husband just informed me he invited a girl he has admitted to liking. She is an absolute doll but a very shady person. She’s also my third cousin if that matters. We don’t hang out with her but talk when we go out and see her. This set something on fire in my soul! My thoughts are he wants to see her in a bikini because lord knows this mom bod ain’t wearing one in front of our friends! Am I just being jealous or do I have the right to feel this way?