Help me be strong and Not get so angry

So difficult thing- SIL is pregnant- "Again" She says she is 8 months and due next month Here are my issues 1. she told me in april she lost the baby- and wasnt pregnant 2. if the above was true she wouldnt be 8 months pregnant right now 3. she has been pregnant since October- but fails to mention to any family members 4. i had been trying to get ahold of her since May 22- since I had again heard from other ppl that she was pregnant 5. finally hear from her and the below is a copy of the conversation - please tell me if i was too rude- dont forget our wedding is next weekend!!! Marly So you will comment on my status etc on facebook but you havent answered any of my messages since May 22nd - such a piss off SIL hey well i know i havent anwser your qustion but yes iam ... im 8 months i losted the baby and got prego 2 weeks after and i didnt tell anyone because i feel like a dum ass that i have done this to myself again .. anyway im so sorry i should of told you ... Marly Well u told me u lost it in april so that still dosent add up SIL ya thats when i told you guys but i was already prego with this baby i fucked up i should i told everyone right when its happend and now i have to tell everyone .. i dont want to talk about it its not something im happy of that i didnt tell ppl now im 8 months Marly It dosent matter if you are happy about it or not, you full out lied to me about things that should never be lied about and AGAIn we heard through other ppl and then you waited months to respond to me- very disrespectful and digusting that you could even lie about anything like that- are you putting the baby up for adoption-and it dosent matter if you want to talk about it or not if your that pregnant everyone will see next weekend and see that you lied to everyone you would have been pregnant since October!!! and then in april you said you lost it but were allready pregnant- digusting lies Maybe i was to harsh- but this is complete and UTTER BULLSHIT She is digusting in every way in my mind and I never want to talk to her or see her again DONT FORGET She has a gorgeous 5 yr old son, who HER PARENTS have full custody of and she does not- so how can she be allowed a 2nd! and then to lie to me about losing a baby etc Sorry to all my IF ladies who are digusted with this- so am I but im having a hard time dealing with her :S any advice???