Lindsay Lohan -- I Want Nothing to Do with My Half-Sister

Don't count on a Lohan family reunion any time soon -- Lindsay Lohan has ZERO plans to meet her newly-announced 17-year-old half-sister ... in fact, she wants nothing to do with her ... ever.

Lindsay is telling friends, she's 100% done with the "circus" that is her father Michael Lohan -- and does NOT want to meet her half-sister Ashley.

TMZ broke the story ... Michael took a DNA test on national TV to determine whether he fathered Ashley back in 1995 with a former mistress -- and the results came back positive.

We’re told Lindsay has been aware of the paternity dispute for a while -- since it's been going back and forth for years -- but did not know her father had taken a DNA test until we broke the story.

Lindsay has not communicated with Michael since he leaked the recorded phone call during her fight with Dina last month -- and no longer wants anything involving him in her life, lovechildren included.

Lindsay says she's doing much better now without her father's drama -- and she wants to keep it that way.

We're told Lindsay has no ill feelings toward Ashley -- but finds the entire situation "disgusting" ... especially because Michael had the affair while he was still married to (and having kids with) Dina.

For his part, MiLo tells TMZ, "I am sorry to hear Lindsay feels that way. I met Ashley and she is a good kid. But we all have our choices to make in life, as well as our own prerogatives. Who knows, maybe someday things will change. Regardless, I want the best for all my kids."