Younger SIL gossiping to older estranged SIL about us. Help!

Some background: Husband has 2 sisters. The older one hates me with a passion and is absolutely insane. She is emotionally abusive to her brother and has a temper. Typically called a "crazymaker" in psychology. The younger one is okay, but she is a "pleaser" and afraid, along with the rest of the family of the older sister. Since I came into the family, her brother (my husband) and I refuse to talk to her as she just accuses and judges us for everything.

Well his younger sister is 28 weeks pregnant and I am 27 weeks. Since finding out we are pregnant, the younger sister has been more open to me, coming over and talking about baby clothing deals, etc. The older sister has taken to bonding with the younger sister since she has two kids, and money. She gives her advice, is throwing her a 2nd baby shower and giving her hand me downs. Which is great and I have no problem with this. However Younger sister often complains and worries about how she will be able to pay for everything and how her sister is taking over.

Anyway, older sister recently tried to reconcile with my husband, but with a really insane email accusing him of being hurtful, selfish. She threw in little jabs about how she heard we were married "because I was pregnant and for insurance reasons" , which is false. She also seemed to know that we initially wanted a boy but are having a girl. She called us terrible people, etc. We've responded to nothing aside from my husband replying he's happy and wants nothing to do with her. She continued to email him, texting me calling me a "shit stirrer, drama queen,etc.". I've pretty much ignored her, as my baby doesnt move much when I am stressed, so I try to stay away from it.

Anyway, my concern is the younger sister. She obviously is getting guilted and probably enjoying her time with her older sister, which is great. However, I fear she gives her older sister info on us, and sometimes even makes up things to keep the older sister's hateful energy focused on us and not on her. (Older sister hates her boyfriend).

Arg! Haha, so that is most of the story, there's a lot more but I don't really think it's useful.

My questions are, why does his older sister hate me? Should I talk with the younger sister and ask her to keep our infornatione private and refrain from speaking about us?

I felt very closed off last time I spoke with younger sister. I never talk to her about it because I don't want to drag her in the middle, but talking about us etc is annoying. I put her on "restricted" now on Facebook but don't know how to approach things without being fake from now on as I find her weak and distrustful now. I really enjoyed having a pregnancy buddy but not when things get talked about and twisted. I pity her so I am not upset but just unsure.

Help! & thanks for reading.