Sister in law ruining marriage life

I had deleted my account on whatsup bcoz of my sister in law creating problems in my married life. I had fed up with her complaints to my husband that I don’t reply her msg quickly or I don’t call her etc, she is so free in her life, but I have lots of work in my life I can’t be online 34 hours to entertain her. But she always take this point against me m tries to show that I m bad to my husband so I deleted my whatsup account only as she always used to post negativity meg to me also. But now she has created one group named “sister in laws “. And added my husband number in that group and introduced that number as mine number. Now she is continuously asking in that group about me my life as if she is more freindly to me and tries to find be out about my life etc. my husband is forcing me to reply all her messages from his mobile as now she added his number. But I don’t want at all to be in that group. I don’t have husband support in such cases Bcoz I knew as Usaual he will debate me very badly for not talking to her sister. Someone please suggest how do I get relief from my sister in law social media torture. As I had already suffered becoz of her social media torture a lot . She had created lots lots of misunderstandings between me and my husband, So someone please advice me Eagerly waiting for response.