She's not portrayed as a novice in the first three aside from maybe Baelish & Varys who're likely to carry that opinion of all the court. In book 4 she's wild but it is just after having lost her son, I think Tyrian's quote is something like "she makes stupid decisions when she's angry", granted she gets her fingers burned by the faith militant but we've not seen how that plays out in the books yet. I don't get your point because Tyrian, Robb, Baelish, Varys even all have made errors.
Anyway this is a TVs version Martin has said a few times the books are the books this is it's own beast, for me she's a great character who you grudgingly respect dispute wishing death upon her, Lena Headey has been magnificent from word go also I think she'll go down as an all time legendary to villain.