Whether to report someone receiving extraordinary levels of help for PhD
Getting help is in and of itself not a problem. Proof reading is perfectly fine. Discussing research with others is very much a part of doing research, so having a sparring partner is a good thing. Even finding and reading papers is not a problem if person B is just interested in the research and the discussions. So a lot of the things you mentioned are not necessarily problems. 

If B wrote large portions of the text and A fails to clearly mention that, then that is a problem. But you will need proof before you can take action.