Anne Bradstreet addresses this occurrence in the poem "The Author To Her Book." In the poem, she directly addresses her writings, rather than her brother in law, using metaphor to imagine them as her children, "snatched" from her side too early and before she was quite sure of them. She describes her brother in law, in a cloaking collective term, as "friends, less wise than true."
This seems to suggest that she does not feel betrayed, as such, by what her brother-in-law has done to her, or at least that she does not feel that he had any malicious intent. On the contrary, she knows that he is "true," or loyal to her, which implies she feels he wanted to have her poems published because he knew them to be worthy, and that she would not be brave enough to publish them herself. However, she also describes her brother-in-law as being rather less "wise" than he is loyal. She seems to feel that his judgment of her poetry is flawed. Personally, her poetry sets her "blushing," very aware of all the "errors" in it which now leap out to her. She feels that it is still "unfit" to be seen by others, and that her brother-in-law was carried away by his loyalty to her and thus unable to see that it was not ready.
At the end of the poem, there is also an implication that money was behind the publication—Anne describes herself as the "mother" of the poems, and says that her poverty was behind the early release of her "children."