The gemara concludes that we make her hold on to the korban mincha to tire her out so that she will be more likely to admit her guilt and not bring the korban mincha so that she will not be killed by the sotah waters. This implies that even after the name of Hashem is erased we try to get her to admit rather than to follow through with the process. Tosafos asks that the gemara on 7b indicates that once the name of Hashem has been erased, we try to get her to drink and no longer attempt to deter her or to sabotage the process? Tosafos answers that it must be a machlokes.
According to rashi's explanation on 7b the question of Tosafos is answered. Rashi indicates that even after the name of Hashem is erased we would theoretically continue convincing her not to drink, but we can no longer use scare tactics because we are concerned that she will be afraid to drink even if she is innocent and remain assur to her husband forever unnecessarily. But, the gemara here is speaking after she already drank and is saying that we would still try to convince her to admit her guilt rather than to drink the water and be killed. At this point there is no longer a concern that she will remain assur forever even if she is innocent because she has already done the scary part which is the drinking. Unless she would admit her guilt the process would continue and verify her innocence, and we therefore try to get her to admit her guilt if she is in fact guilty rather than be killed by the waters.
Tosafos who considers this to be a question must have understood the gemara on 7b that after the name of Hashem is erased we want the process to follow through (perhaps because it would be a tikkun for the erasing if it was not done completely in vain). Therefore Tosafos understands that the gemara here which implies that we try to stop the process even after the name has been erased (and she already drank) contradicts the gemara on 7b.