Some purists may have doubts about the battles in Mirkwood, but they are mentioned in the Hobbit. We are told that Gandalph just managed to escape the Necromancer, Sauron, but the film has Gandalph imprisoned, which is not faithful to the book. However, the Hobbit does have Gandalph speaking about his role as part of the White Council that drove the Necromancer [Sauron] from Mirkwood, so when this became part of the film it was at least true to the text, even though the Tolkien did not include it in the narrative.
The character of Tauriel is another addition to the text, though as the actress who plays here points out, Tolkien never says that the elves are exclusively male, and this is a valid point. She plays her role well and despite being an addition to the text viewers will feel that her presence adds to the film.
There have been criticisms of the role of women in Tolkien, but feminist criticisms on this matter are in general misplaced. While there are few women in the text, none are stereotypical. What few women are present are strong characters not given to talking only about men and babies. Tauriel is such a female, a warrior maiden with a strong role in battle. However, I found her affection for the dwarf Fili an unwanted addition to the Tolkien narrative. Tolkien was not a romantic writer.
In fact, many people do not realize that the Middle Earth tales are war novels derived from Tolkien's experience of World War 1. Thus they are very much about male combat fellowship, the bonds that grow between warriors who fight together and the inevitable grieving for the fallen. They are therefore unavoidably male books. I think it important that political correctness be not allowed to impose a formulaic politically derived gender division upon texts. While books will normally have a blend of male and female characters, it is inevitable that some books will have more of an emphasis on one sex over another. Some will be told from a male standpoint, and others from a female one. This is to be welcomed as an expression of diversity.