The woman brings two sets of liars, or perhaps they were just unable to recall every detail correctly and were telling the truth? Rabbis Tarfon and Akiva in Makkot 1:10 said that if they had been on the Sanhedrin no one would have been executed, which is taken for- they would have asked questions until they found one that witnesses could not answer. If so, we are not talking about liars but inadequate witnesses. It would have been much more difficult and rare to prove a witness was lying rather than tripped up, unobservant, or forgetful. Is this Mishnah actually talking about liars or disqualified witnesses? If disqualified witnesses then the woman should be able to continue bringing as many as she likes. If she brought found intentional liars, wouldn’t they be executed and this would greatly discourage more false witnesses, making it unnecessary to ban the lady from procuring more sets, especially after a second set was executed?

The Gemara uses the term ואישתקור, which clearly implies that the witnesses were found to be lying, not merely that they were asked difficult questions which they were unable to answer and were therefore disqualified.