Wtf seriously wtf, why is Oda making things more and more easier for the alliance.
Based on the spoilers I don't think Big Mom actually turned back to O-Lin, however it seems like Oda is going to use Big Mom and Tama's friendship to have Big Mom help the alliance.
First you have a majority of the SMILEs switching sides, then you have some of the Waiters and Pleasures switching sides, and now it looks like Big Mom will switch side and if Big Mom switches sides then Perospero will probably do the same and help the alliance.
Also Tama is a horrible plot device, Act 3 started off good and now it's going downhill.