...if I tried to approach her family when I get back they would "Make it clear that they want nothing to do with me."

Yep, more manipulative threats and bluster from her. Until you hear it directly from your MIL & FIL, I would just ignor what she says.

Funny how your MIL wrote you yesterday thanking you for the new computer for her other daughter's wedding present... doesn't sound like she was "making it clear that she wanted nothing to do with you", does it?

Focus on the facts, not on her poor attempts to manipulate you.