My bird has diarrhea and is sleepy

Hi, I am quite new to this, but I really need help with my budgie Kiwi.
She will be 3 in six months and lives in a cage with a male budgie. They mainly have seed and fresh veg/ fruit diet.

She has been having watery droppings for about a week, but she was acting very normal, playing, chirping and eating normally. I thought it was due to some greens I've been giving them. She has always had a bit more watery and greenish color poop, ever since I got her. It was never a problem, she was acting the same as the other bird, maybe a bit less active, but I thought it's down to the fact that she's female.
A few days ago she was acting very sleepy and I noticed some undigested seed in her poop. I got worried and started to mix her water with cider vinegar, to see if it improves. It didn't do much so I ordered probiotics. After two days there was no improvement and she got worse.

She bobbs her tail a little and her breathing seems a bit hard, like she moves up and down a bit when she's breathing. But again, she was like this from the day I got her, and I thought it's normal and just her nature. She's been alright for the past 2 years so I never had a need to take her to the Vet.

When I woke up on Sunday and saw that she looks very weak and very sleepy I tried to offer her some food. She wasn't interested in food at all. Her droppings got worse, even more watery. I booked an emergency appointment to the Vet and was there in a few hours.

The vet examined her and said that she might have an egg, as she was breathing a bit heavily and she sensed something hard around her lower stomach area. She said it could also be tumour or some kind of inflammation. The only way to find out and treat appropriately would be having an x ray which requires anaesthesia and it has its risks, especially as she's quite weak atm.

I am very scared about an X-ray and had a bad feeling about it. I said I will wait one more day to see how she gets on. Kiwi got prescribed some antibiotics, pain killers and calcium.

I set up a hospital cage for her and separated from the other bird (which I think is a bit stressful for both of them). I've been giving her medicine and the next day she looked much better, she ate from my hand- broccoli, pear, seeds and millet. She was also chirping and even moving around a bit, but still was quite sleepy.

I put her in bathroom and ran a hot shower, so she is warm and comfortable. The vet said it might relax her to lay egg if she has one. I also got a nest as advised. I have feeling that it's not an egg, as she had a bit of these symptoms back in January but without watery droppings, I was also thinking she has an egg as she was kinda expanding her womb and sitting in a strange position. It passed in a few days.

Today she is the same- eats a bit if I give it to her. She preens herself and even chirped a bit. She doesn't seem as weak. I have uploaded a photo of her latest droppings. The only thing that concerns me is that she sits with her eyes closed so much and was even shivering at some point, even if I keep the room super warm. She doesn't move around, just sits on her favorite toy and occasionally has a drink or eats something. She was on the bottom of the cage eating sandpaper. I heard it might help their digestion? Maybe that's the reason she does that.

I am still very worried as I'm not sure what to do. I want her to get better, but not sure if this medicine will be enough for her. I am also scared of going through with an X-ray, as I would hate myself if she wouldn't wake up from it.

Do you think she has some kind of illness? Could it be temporary?

I appreciate your help!!!!