Betta breeding is hard work, and expensive in terms of money, time, and space.
Is she near a male at all? If she is, and she's ready to lay eggs, she'll display vertical dark bars along her body, although general colouration can make this an unreliable point.
If she's not, and she does have eggs, she'll simply discard them after a few weeks of carrying without male contact.
To tell if she's carrying eggs, compare her to other females of similar size, and see if her midsection looks overly bulky.