Powershell Script:

$Groups = Get-Content "C:\Scripts\Groups.txt"
$Players = Get-Content "C:\Scripts\Players.txt"

Clear-Variable -Name "PlayerGroups"

$PlayerGroups = New-Object "System.Collections.Generic.Dictionary[String,String]"

foreach($Player in $Players)
{
    $RandomGroup = $Groups[(Get-Random -Maximum ([array]$Groups).count)]
    $PlayerGroups.Add("$player","$RandomGroup")
}

Write-Output $PlayerGroups | Sort-Object


Output:

Key     Value
---     -----
PlayerA GroupB
PlayerB GroupC
PlayerC GroupA
PlayerD GroupE
PlayerE GroupE
PlayerF GroupA
PlayerG GroupB
PlayerH GroupE
PlayerI GroupB
PlayerJ GroupB
PlayerK GroupD
PlayerL GroupE
PlayerM GroupE
PlayerN GroupD
PlayerO GroupD