And I can think of quite a few which are nothing to do with her being the victim of abuse and/or coercion. Not every woman who behaves badly does so as a result of abuse.
In this case, I think there are several factors which would tend to suggest that she is not a victim of abuse or coercion. Firstly, why on earth would she tell her abusive husband’s sister- to whom she is not close, from what op has said- that she was covertly using contraception whilst pretending to him she was on board with TTC? That makes no sense at all, surely his family would be exactly the people most likely to tell him (especially if they have no idea he is abusive)? Why would someone terrified that their abusive husband would find out about such a significant deception tell the very people most likely to tell him her secret? She would be highly unlikely to make that choice, unless she was very close to her SIL and was confiding in her about what her brother was doing/swearing her to secrecy or asking for help. if she did want to confide in her out of desperation, to gain her SIL’s support to help her out of an abusive/coercive situation, then I seriously doubt she would have gone about it in the way OP outlined in her OP and gave more details about in her subsequent post (I.e, by laughing/giggling).
The stretch to get this to be all the fault of the man is quite something. Abuse and coercion by men towards women is far too common, but we cheapen it and do genuine victims no favours when we try to call anything and everything abusive and claim women can only ever be the victims and can never, ever just be in the wrong. You are aware that women can be deeply unpleasant people too? That sometimes women are selfish, manipulative, lie for their own gain etc? Women are not always victims, they are not always in the right and they are capable of doing horrible things.
In this situation, I presume the reason she is lying to her husband is either that she wants to stay married to him but knows that not wanting children is likely to be a dealbreaker for him, or possibly because she gets a kick out of leading him on. I think the former is a more likely scenario. I can imagine that if she knows/thinks that her husband would end their marriage if he was aware that she does not want children at all, or cannot commit to wanting them in the future, but thinks he probably wouldn’t leave her if one or both of them was infertile, that she might then have gone down the line of faking infertility either hoping he would just accept it as “not meant to be” until she is beyond the age of conception (if she never wants to have children), or until she changes her mind (if she is just not keen right now). Thus keeping her marriage intact, whilst also not having children she does not want. Or, perhaps she has a reason to want to stay married right now- this could be financial, for instance- but knows he might end their marriage if she was honest with him, and so has chosen to string him along by pretending to TTC, until it suits her to end the marriage (or she changes her mind). Or, she just enjoys the power trip/playing games etc. Some people are just horribly manipulative, for no other reason than to show to themselves that they can/to make them feel important or to get what they want, regardless of the harm they cause to others. Women are not immune from any of these awful behaviours.