With as much as she is straining, the odor may be from small amounts of urine or fecal material that is getting onto her hair. That may be why she is grooming so much, to try to clean herself up. Is the swelling around her back end at her anus? If so, that could be an accumulation of stool, and that could contribute to the smell too.
Especially since we don't know whether the primary problem is urinary or fecal, or what the underlying cause is, there's not much I can recommend you do at home. Make sure she is eating and drinking. If she doesn't feel good and doesn't want to go to her bowls, try taking the food
and water to her and see if you can encourage her to eat and drink. If she won't eat her regular food, you can even try things like canned food, tuna, chicken, or meat baby food.
I'd recommend getting her in to see your vet tomorrow if possible. If she starts to act very sick, like not even wanting to get up or not responding to you, you may even need to consider an emergency clinic tonight.