My Wife Hates My Son

I've been married to my wife for almost a year. A few months ago my 13 year old son moved in with us because his biological mom didn't want to deal with him (which I do not understand). My son is a good kid but a typical 13 year old with a bit of a smart mouth and little common sense (just like his dad at that age). My wife is an only child and spoiled out the yinyang. She's 41 and still gets a monthly allowance from her parents, you get the idea. My son has done little if nothing to upset her let alone give her reason to despise him as much as she does. My wife and I have had issues in the past (arguing) but have recently gotten to where we get along really well. Last night she told me she wants my son to move out of her house (yes it's HER house that I pay for). I told her sorry, if he goes I go (no brainer) and she seemed fine with that. I'm currently looking for a place to live. My question is; is this a jealousy thing with my wife? I ask her why she hates my son and all she can say is that "he's annoying" (what 13 year old isn't). I'm thinking that she is jealous, wants her "old" life back and now that she has a job (she hasn't worked in over a year while I put her through nursing school) wants to be independent. She's emotionally immature and has no real understanding of life. She's never lost a family member or had to suffer the regular hardships most of us do by the time we're 20. I'm hurt by this and saddened but I'm not about to betray my son for anybody especially a spoiled brat.