Not really, if she had wanted to kill her "rival", she could have bought a handgun or other firearm in just a few minutes in any gun store, sporting goods store, or pawn shop in the Greater Houston area. Instead she took a fake gun. To me that's evidence of wanting to scare the other woman, not kill her. Kidnapping is still on the table, attempted murder is not.
She did everything possible to avoid leaving a trail. Purchasing a gun would have left an obvious paper trail.
If she was looking to scare and not kill; what were all the garbage bags for? Was she planning to win the rival over by offering to clean all the old fast food wrappers out of her car?