R-E-S-P-E-C-T

How do you teach a 4 year old respect? I am struggling to teach her at her level what respect means. I know that I lead by example and am not always the best. There are times where I raise my voice. Then, when she does it, I am taken back and wonder why? This morning she was yelling at me because she wanted to wear a dress. A few weeks back I sent her to daycare in a dress... she came home with pants on under it because she couldn't keep her dress down. So, naturally when she asked to wear a dress today I said 'no' (not to mention it is not very warm outside). Well, this didn't go over well! She preceded to yell at me. Then while I am fixing her hair she says... "You have ruined my life!" I asked her if she even understands what she is saying and she says "doesn't matter my life is already ruined!" At this point I decided to take a break before it escalates even further. I know in my heart that she doesn't mean nor understand what she is saying. What I want to teach her is two things... 1) we show respect for our mothers 2) if you treat others that way you will not have any friends. So I am asking for your advice or suggestions!!