Rav Moshe ruled that her conversion was completely fine, on multiple grounds:
- She is not believed insofar as believing her would make her forbidden to her husband and cast aspersions on her children.
- Her alleged thought counts as דברים שבלב, which cannot outweigh her explicit statement to the בית דין administering her tevila that she was accepting all of the mitzvot.
- If a convert were to say that he was accepting all of the mitzvot but he did not think he could withstand a יהרג ואל יעבר situation, his conversion would be good anyway. Rav Moshe brings three proofs for this point (including the fact that someone who converts for marriage purposes is considered to be a valid convert, even though such a person is certainly not thinking of giving up his life for mitzvot), and concludes that the fear of losing one's job is a similar pressure that many people have a hard time withstanding, and thus it should not invalidate the conversion.
- This woman had been living a strictly observant life for the past ten years, a fact that was known to all, and thus her initial transgression was clearly not indicative of a lack of a desire to keep any mitzva.