Why Does My Fiance Get Mad At Me For Nothing At All?

It seems to me that your fiance may have something going on that has not been dealt with. Meaning that maybe she doesn't feel acknowledged and loved enough verbally? Something is wrong. Even though your first response was to get upset at her after she yelled at you (which is normal and to wonder "why") take time to sit down and talk with her and explain to her that you were trying to help. Help her to feel safe with you emotionally. She may have been hurt in her past or maybe it's more recent. When she opens up to you in conversation allow her to say what she needs to and don't cut her off. Otherwise she'll feel that you aren't really listening to her.

An eruption of emotion means something has been building for at least a little while. When you sit down and talk with her keep the mindset that this is about her... not me and listen and validate how she is feeling. You will both get through this. Take care.

It doesn't always have to be a "deeper issue". It seems to me while just looking at the scenario you laid out for us concerning her "snapping" when you came out to help, it wasn't that big of deal. She was obviously already stressed while trying to remove the bugs from your car and you broke up her concentration. Your fault? Of course not, I know you were just trying to help but her reaction (although not very nice) was completely normal.

We as humans react on impulse a lot so before she had time to run it through her head calmly of what she should say to you, she "snapped" instead. It was just one of those days, no biggie. I believe it is very unhealthy if we don't have arguments in relationships. Now if this is something that happens every single day, then you may have a problem you two need to work on. But considering just that one episode, it's more minor and "normal" than you realize.

It sounds to me like you weren't the one who provoked the argument. Sometimes people tend to overreact and explode because they had a bad day. If this is a constant issue I would sit down and talk to her about it, letting her know how you feel. If she still doesn't care I would seriously re-consider the relationship. Communication is the key to every successful relationship. A prenuptial contract could be a good idea.
www.aprenuptialagreement.net

Or maybe she just having on of those bad days. Try asking her "what's wrong?' "are you ok?" "Is there something in your mind?" I think she just wanted to surprise you by washing the family car. Or sorry to say this (codydino) but maybe she has a high blood pressure??? My friend acts the same way. Please have her check at the hospital, and if I'm wrong then I'm truly sorry......