If Maria is not represented at the time of the conversation, Karen appears to have violated Rule 4.3 because her conduct during the conversation implied that she was disinterested and she did nothing to correct that impression. Her conduct was deceptive and devious. Karen might argue that the information that she obtained from Maria is in any case discoverable, and that she would have learned it during the pre-trial process, so no harm was done. She has no information that would help her that she was not entitled to anyway. Her alleged violations of the Rules, she might argue, should not be used to get her removed from the case.
Courts routinely apply the standards laid out in the rules to help decide disqualification motions.
The rules forbid her to help further this conduct. Karen could be helping a witness to testify falsely. On the other hand, Larry says that there are good days and bad days. Note that here Rule 1.6 is specifically subordinated to the requirement not to mislead the tribunal with false evidence. She might threaten Larry with disclosure of the truth if he does not testify honestly and then withdraw if this threat is unsuccessful.