The very upright stance is often a symptom of being egg-bound, even if there's not noticeable swelling like an egg ready to plop out. One quick and easy thing you can try is to give her a warm bath. Fill your sink partway (or a dishpan, if you'd rather) with bathwater-hot water (if you like hot baths, that's the temp you want, if you like cooler baths, make it slightly warmer than you would prefer for your own bath). Set her in it, where her bottom and abdomen are in the water. She may actually settle in to the water comfortably, like it feels good to her, or she may argue with you and decide you need the bath, instead, but if she is egg-bound, it might allow her to pass the egg she wants to pass.
I would strongly advise to lift and move her carefully, though, because if there's an egg in there "stuck", you don't want to break it. That nearly always ends badly when that happens.
Good luck! Keep us updated. Hopefully the bath works out well, without any further intervention.