Do you have any other chickens you can feel for comparison? I find that feeling a healthy chicken is one of the fastest ways to tell if something is normal.
The neck of a chicken can make an odd sort of lump, and the crop makes a lump too. So those are at least two normal things that might be making the lump.
If you really cannot tell, watch how the chicken is acting, then pay attention over the next day or two. A crop gets more full when the chicken eats, and less full when the chicken digests the food (especially during the night). Checking for those changes is a good way to be sure where the crop is.
Crops are the place where food goes after it is eaten. They fill up during the day, and then empty overnight by the next morning. It does look like her crop is full. Check it again in the morning. How is she doing? Can you describe any symptoms? Are there any wounds? Is she holding her head up normally? Can you give sips of sugar water or electrolytes, and offer wet chicken feed and some cooked egg? Can she stand up and walk? Do you have her separated?