Why people have to lie?

I just hate people lie to me. I got pissed at my helper this morning coz she broke the wine glass. I didn't get angry because the glass broke, I got angry at her coz she told me before I asked her about the glass that the glass was broken already before she washed it! So, who broke the glass then?! Few months ago, she ruined my pants by putting a chlorine on it, and I expected her to say sorry about what happened instead she told me that there was chlorine stain already before she washed my pants! What?! So, I told her that the pants that she washed was never been washed before coz it was brand new. Why she has to lie? It made me angry.