Before 850 I didn't think she was evil but I didn't say it was impossible. The thing is now is that there are a lot of things that don't necessarily add up. I know a lot of people have noticed them but a couple are:
1: We were literally shown her thoughts and it seemed like she was genuine. Why would she think in a nice way when she is completely evil?
2: There were times where she was alone and she still acted nice.
3: Does anyone question BM's motive in killing the Vinsmokes? Like to me it makes 0 sense. They are gonna be allies meaning that basically BM gets all of their information. Including the clone formula.... and even if they didn't she could just threaten to destroy them or maybe even have them manufacture the clones for her. Killing them is an unnecessary extreme and almost all that we have seen of BM shows that she doesn't always go to the unnecessary extreme.
4: I think its kinda weird that Oda just decided to throw in that line where it shows that Pudding is actually kinda frustrated at BM. Like its not really necessary to say and i think it could be hinting at the fact that she is not working for BM but rather herself in an attempt to get away from BM. Maybe even helping Capone with his plan.
5: Last but not least is the fact that she is telling Reiju her entire plan. Why? The only thing that I see that would mean that she is on BM's side is if Reiju somehow saw her break character... which considering her acting skills throughout this arc seems rather suspect. Unless she intentionally let Reiju in just to let her go and turn the Vinsmokes again BM. In which case she could be trying to help Sanji as promised or she could be trying to get away form BM. Then why did she tell Luffy and Nami that they were going kill Sanji? To me that scene means that she is 100% evil just because she did it just to piss him off and get him mad. There were zero tactics in that move considering Luffy is all but taken out of the game. so she did it for sadistic reasons meaning that she is evil and has her own plan to get out of this wedding.
So basically my running theory is that Pudding is trying to get away from BM and she is using the people on the island to do it. I mentioned before that maybe she is working with Capone to get away and is gonna use the Vinmokes and SH to do it.