Thanks for the answers to my questions and the pictures (which are very helpful, by the way)although I'm sorry I was off my computer when you did so.
I have several thoughts as to what might be going on with her and while I typically try and explain all of a patient's symptoms with one condition, it sounds as if that's not likely to be the case for her.
I understand about not being able to take her temperature although it's always helpful to know if the patient is running a fever in situations such as this. Even though she may feel warm to the touch, her core body temperature may not be elevated. If you do somehow manage to take it, normal is 100-102.5.
1. Given her propensity for chasing and snapping at bees/insects and the acuteness of the swelling on her muzzle and the bump you're seeing (which are obvious in the pictures you sent), I'd have to suspect that her facial swelling and the eyes issues are secondary to an encounter with one of these flying critters. This could also account for some of her lethargy as well.
If this were my patient, I'd advise an over the counter (at least here in the States) antihistamine such as Diphenhydramine at a dose of 1 mg per pound of body weight twice a day which would be about 75 mg for a dog this size. This drug comes in 25 and 50 mg here in the States so I'd give 1.5 pills of the 50 mg size. Sedation, unfortunately, can be seen as a side effect though so if she's already somewhat lethargic and she worsens, then you won't know if it's because of the drug she's taking or something else is going on. However, I might be tempted to give her one dose since this is often all that's required for many patients with anaphylactic reactions of this sort.
If the face and eye issues are what I think they are, then you should see improvement within just a few hours.
And, in case you were wondering, there shouldn't be any contraindications in giving Diphenhydramine concurrently with the other drugs she's taking.
2. As far as her loose stools are concerned, I suspect the antibiotics she's taking to be the culprit. It might also explain her lack of appetite since gastrointestinal signs such as diarrhea, anorexia and/or vomiting are commonly seen side effects. The yellow you're seeing simply reflects increased transit time and not anything to worry about.
I wouldn't suggest that you discontinue her Synulox but I might feed a bland diet of boiled, skinless, boneless chicken breast and 20-minute white rice for now. I'd also start a probiotic such as Forti Flora (available here in the States although I'm not sure what you might have there).
Her stools may continue to be soft the entire time she's taking the antibiotic but should return to normal once they're discontinued if the probiotic and bland diet aren't effective.
Hopefully, she'll find the bland diet more palatable than what she normally eats but if she's hardly eating anything, then I wouldn't want to continue giving her this drug on the off chance that it's the problem. If the antibiotic is discontinued and she still doesn't want to eat, then something else is going on.
3. I always worry about a uterine infection (aka pyometra) when an unspayed female becomes lethargic and/or doesn't want to eat but it's fairly uncommon for this condition to develop during an estrus cycle. More commonly, it develops 4-6 weeks after the cycle is finished. I wouldn't entirely rule it out but it wouldn't be at the top of my list either but I'll include it to be complete.
These patients can run fevers, their appetites can be off, they can be lethargic, they may be drinking more water and they often have a yellowish, pussy vaginal discharge.
This condition would be considered fairly serious since if left undiagnosed and untreated, the kidneys can be permanently damaged.
At this point, I'd rule out the most obvious, possible causes for her symptoms as I mentioned above. However, if she continues to not eat and/or remains lethargic or tires easily and/or she worsens in any way, then you may not have much of an option but for her to be rechecked unfortunately, although it gives me no pleasure to say so.
I hope this helps although, again, my profuse apologizes for the delayed reply. Deb