Cinderella's belly looked like a mess too when she got spayed at nearly 6 months. She is turning 9 months old next month. I was a little concerned because it looked so terrible, but I trusted my vet entirely. Our vet used dissolvable stitches on the inside, and also used regular stitches on the outside. You can imagine how gross it looked. Black stitches here and there on the outside, like a patched up Raggedy Ann doll, and lumpy things all over on the inside.
Coincidently, I was looking at her tummy tonight, and on the outside, it has healed up beautifully. You cannot even find the incision site. As for lumpies, well...she's still got about 2 here and there, but when I pressed on them, she didn't even nudge. I guess that's good enough for me.
For Cinderella, it took months before she looked truly recovered. I'm quite sure, even at the one month mark, she still didn't look normal there. But follow your instincts. If you feel like it was a terrible job, then you have more than the right to confront your vet.
I also have a male chihuahua, Gizmo. Another sweet angel from heaven

Though he is a male, and the surgery is quite different, I do have a picture of him with his "lampshade" over his head the day after his surgery. It looked so awful, I had to take a picture to show my best friend. Was wondering if it was normal for a neuter operation to look so ugly afterwards. I don't know if I'm allowed to post the picture or not here on the forum. Maybe it will be too gross? Gizmo turned out super cute though

It shows him struggling to chew his favorite bone even with his "lampshade" on his head.
If you want, I can email you the pic. Maybe you will feel relieved and assured after. It took, looked like something out of Frankenstein.
Wishing you all the best