You tell the Daycare.
Childcare businesses and schools, cannot just release a child, to whomever picks up the child.
There is a permission form which stipulates who can pick up your child.
If they release a child to someone else, that is, against policy and laws.
And they can get in trouble.
DOCUMENT all the threats, the Girlfriend is making, and that she is picking up your child etc. SAVE the messages the girlfriend sends you. This is, evidence.
Keep documenting, the Girlfriend's actions/and whatever she tells you. Document whatever your Ex is doing, too.
You need to do this. For your own child's protection and per if you go back to court, to dispute anything or change custody.
There are many types of child custody. Research this.
Get a Lawyer. A good one.
Again, if a child care facility or school, releases a child to whomever and to someone that is not permitted to do so... you can report the facility and/or the Police. Perhaps.... filing charges against the Girlfriend... for threats made to you and for attempts to kidnap your daughter etc. or get a restraining order... against her.
If YOU... do not permit the Girlfriend, to be "added" to the custody plan... I would think, your Ex cannot do this.
GET A DAMN GOOD ATTORNEY.
AND CHANGE YOUR CUSTODY PLAN.
Document everything.. about your Ex and his negligence.... you need documentation and proof, about his neglect etc.
And get witnesses, if you can too. For your case.
This is about the law.
Not about the petty personal personality problems between you all.
The bottom line is, the well being of your child... and custody.
But since they "threaten" you... document all of that.
Or get a restraining order against the Girlfriend, and you need to state that you feel "unsafe" for your well being AND your child's.... and you do not feel "safe".... under all these threats against AND your child.
NO you do NOT have to allow the Girlfriend to pick up your child.
And you ARE being threatened. Report this to the Police... that she is attempting to take your child etc.
ie: you said "my child's fathers new girlfriend sent me a message threatening to take my child from me... "
That to me, is a threat.... and it can be taken that she can kidnap your child... against your wishes.
And by the way: Be "smart" in the order in which you should do these things, if you choose to is: file charges against the Girlfriend for whatever threats she made to you and your child. THEN, go to the court and change custody etc. Be wise, in the order of things and what is done first or 2nd etc.
If you want to change custody and who can pick up your child or not... it would make more sense, that if you have a restraining order against Girlfriend first... then it might be easier for you to then, change your custody. Because, documentation/proof would already be filed with the Police.