MIL and SIL rant

So my mil has been so mean to me lately because apparently when she's bored that's what she does. Yes, a 65 year old woman acting 12. She's been getting on us about our wedding which we had a civil ceremony yesterday just so she would shut up about how we were planning it. 
Anyways, my hubby's sister is 35 and been with her boyfriend for about 4 months. Yesterday she just found out she's pregnant. Is it mean of me to be a little mad?! We are trying and haven't gotten anything yet and then someone who hasn't had a job, no place of her own, I am just so confused why someone like that would be blessed with a child and not someone who is actually trying. 
Life just isn't fair sometimes 😕