This sounds like the ideal situation for Divorce from Bed & Board.
“What is divorce from bed and board?
Divorce from bed and board is a fault-based action, usually brought by an injured spouse to get the court to order the other spouse out of the residence. If brought in conjunction with other claims (custody, child support, distribution of property), a judicially ordered separation pursuant to the prayer for divorce from bed and board establishes the separation required for those other actions. The complaint for divorce from bed and board must be verified and it must contain the required allegations of residency.”
“Who can file for divorce from bed and board?
Only the injured party may apply for a divorce from bed and board”
“What fault grounds can be used to file for divorce from bed and board?
The complainant seeking a divorce from bed and board must establish at least one of the six fault grounds enumerated in the statute: abandonment, malicious turning out of doors, cruel or barbarous treatment, indignities, excessive use of alcohol or drugs rendering the condition of the other spouse intolerable, or adultery. Further, the complainant must allege that he or she did not provoke the other spouse’s misconduct. The right to jury trial in an action for divorce from bed and board is governed by the statutory provision permitting a jury to make the factual findings on issues of fault.”
My suggestion is to gather all the information “proof” you have, all the stuff you mentioned (messages, dates that she stayed away from home overnight) and take it to your attorney. Also, file for primary custody, equitable distribution, and child support. Document everything. Talk to your neighbors, if you have them…I understand how difficult that is but they will obviously know about her behavior and may even know more than you think. They may be witness to her having her “friend” in your home and be willing to tell the court that.
Most importantly, protect yourself finacially, and take care of those children. There is no easy way to go through a separation/divorce and the children need at least one stable parent in their life.