We NEED HELP with our 3 year old granddaughter displaying unusual behaviors.

May 2021
HELP! One of my Granddaughters, "SAM" (3 yrs) has been displaying a maddening behavior in our home, and we would like suggestions as to the cause, (what triggered this behavior), and/or creative ways to fix this. BREE has 3 children with a man her own age ( a Boy, age 5. a girl, "SAM", age 3. and a Girl age 1.5. ). Until a month ago they all lived in a house he owns in Southern Ohio, which is a 2.5 hour drive from our home in mid ohio. The boyfriend started drinking beer too heavily, and I offered for BREE and the 3 children mentioned above to come and stay in our home. There are many situations happening with these children currently, but the one that needs immediate attention is this: SAM absolutely must have her mother in her line of sight at all times. If BREE leaves SAM's line of sight, SAM chases after BREE, screaming at the top of her lungs. SAM doesn't appear to want to be picked up, or cajoled in any way after she reaches her mom, she seems to want her mother to stand still, and is absolutely (guttural screaming) adamant that BREE remain in one spot, in whatever that room may be, at all hours of the day and night. SAM also performs this behavior when her mother goes in front of the two cabinet doors underneath the kitchen sink. When BREE happens to approach the sink, SAM raises the volume on the screaming, and rushes in front of the 2 cabinert doors directly below the sink, as if she is trying to prevent her mother from getting in front of the sink, or the 2 cabinets, which we are not sure. BREE is unsure of how long this screaming has been happening, but it was definitely occurring prior to their arrival at my house. BREE's mother and I split while BREE was in the womb. I played no parental role in BREE's life growing up. She grew up exclusively with her mom and mom's husband. I only met BREE for the first time in 2014, when she was 20 years old, and I was 49. The only plan at the time was to get her away from him and the drinking, because BREE was "tired of it". Brief background/possibly pertinent info:
*The 3 children have never had a bed time. Where they fell asleep is where they fell asleep until they awoke. When queried about why this was, she stated that she never knew you were supposed to put your children to bed at a regular time every night. The boyfriend evidently did not know this either.
* The 3 children have never been "potty trained". Nor have they ever been out of diapers. I have also noticed that BREE does not change the childrens' diapers very much. It seems that they will have a dirty diaper on for extended periods of time... The oldest, upon feeling the urge to defecate, searches out a hiding spot somewhere in the house, takes off his diaper and defecates.
* I do not think any of the 3 children have ever been reprimanded for destroying property.
,if we can correct this one highly stressful and detrimental behavior, or even curb it, it has the possibility of positively affecting other behaviors happening concurrently. Suggestions?