No, not common.
Compare how her belly(from under vent to between legs) feels to other birds.
She could have a broken egg inside, it should pass when the next one comes along.
Most likely, and hopefully, it's a softshell egg and not a broken hard shell that could
possibly cause a cut and subsequent infection.
I'd give it a few days of isolation(for most the day and all night) to observe what she's eating and what comes out of her vent.
If at all possible, put some smaller wire(1x2 works best) on bottom of crate and then put tray under crate(see pic below), that's the best way to observe her poops.
I'm not one for AB's, so have no suggestions..nor have I ever dealt with . If you really think she may have a broken egg stuck and don't want to wait, I'd start a new thread in emergency forum with "broken egg stuck" in the title, you'll get lots of advice there.
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