Hester's main conflict with nature, as I can see it, is that her own persona was strong-willed, passionate, and judging from her many talents, was very powerful and free. Yet, these same attributes that define her are what ultimately doom her: When she had the affair with Dimmesdale it is not clear whether she was grieving as a widow, or not. We do not know if how she reacted when she found out she was pregnant. All we see is a very stoic woman who stops at nothing and whose fiery temper was clearly obvious when she had to defend her right to keep Pearl.
Yet, women in her time were to be seen and not heard. How could have Hester fit it? Her nature was simply not built to be a woman of her time.
Another conflict with nature is the birth of Pearl. If nature had not intervened, would've Hester continued her affair with Dimmesdale? He was a clergyman and she did not care about that, so, was it all because of a flop of nature exposed her?
In all, Hester and nature do not mix. Nature exposed her, and punishes her daily.