Paul Walker's Mom In Legal WAR With Meadow's Mom

3/27/2014 12:45 AM PDT

Paul Walker's Mom In Legal War With Meadow's Mother

Paul Walker's baby mama has taken 15-year-old Meadow from the family home ... and Paul's mom is going to wage legal war in court today ... TMZ has learned.

Meadow had been been living with Cheryl Walker since August -- 3 months before Paul died.  After Paul's death, Meadow's mom, Rebecca, flew from Hawaii to live with Cheryl and Meadow and planned to stay until things stabilized.

But TMZ has learned everything fell apart last week when Cheryl filed to become Meadow's legal guardian.  Rebecca was pissed, and took Meadow to live at a family friend's house a mile away from Cheryl. 

Rebecca has had a serious drinking problems over the last 6 years, with 2 DUIs under her belt.  We're told that's why Meadow reached out to her dad several years ago and asked to move to his home.

And, in Paul's will, he expressed the desire to make his mom Meadow's guardian in case he died.

So Cheryl will go to court today in an attempt to win temporary guardianship of Meadow, but family sources tell us Rebecca will fight her tooth and nail.  Our sources also say ... Cheryl is armed with evidence that Rebecca's drinking problem has not subsided and she's an unfit parent.

It should be interesting ... Rebecca has a legal advantage because she's the biological mother, but Cheryl is determined to protect her granddaughter.