I despise my sister!

I'm currently 14 weeks pregnant and recently found out that my sister is pregnant as well. Since my parents practically raise her 2 year old (he's there 5 days and nights a week), I find it aggravating that she's not only pregnant, but she expects everyone to be happy and supportive of her. 
Might I mention that she's 20, married but not to the guy who got her pregnant this time, she doesn't work- she lives with the new baby's daddy and lives off of him, and she dropped out of highschool when she got pregnant with her first one just before she married his dad who is an illegal immigrant. 
My mom had an aneurysm 2 years ago and she has been told to keep stress to a minimum to avoid another one and the stress my sister put in her life with all her drama makes me worry that there will be another one, which much like the last one, I blame on my sister. 
I don't know what to do anymore. I don't go to family functions because I can't stand to be around her, I'm actively searching for a home in another state so I don't have to be anywhere near her, and honestly, I wish she would drop off the face of the earth.