Family behaviour?

What is your opinion if you wife to be sister was pressurising your partner and trying to control her and accuse her of things.

We are due to get married but over the last few months my partner has changed at the weekend my partner broke down and I took her phone to stop her deleting her family. When I took the phone I saw a message that concerned me where her sister was saying that she did not care about her daughter and was only interested in getting married.

This could not be further from the truth as my partner gives everything she has to her daughter, mother and this said sister.

I wasn't going to say anything but I could not hold back as this has nearly Brocken us.

I have and her sister has tried to spin what I said by cherry picking parts of messages to post to the family. This has created and big problem between my partners sister and me.

I have defended my partner and myself.

What would you do and how would you handle this?

Family behaviour?
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