Not a Regex expert, but I like to play.

Here's the horrible pattern I came up with. Plug it into your Regex site link and see if it works for you.

(^[^\d\r\n]+?)( +)(((([6789])|(\d{2,}))min\r?$)|(now\r?$))


Or here's a VB solution. I've given each group a name to make it easier to retrieve the required data. The input sentences are slightly different from yours, in order to show that time values less than 6 are disallowed:
Code:
Dim sentences() As String = {"A is on phone from last 5min",
                             "B is on phone with A from last 7min",
                             "D is ready to talk to C now",
                             "D is 1min closer to talk to C now",
                             "E is waiting for D forever",
                             "F is waiting for G to pick up phone from last -12min",
                             "F is waiting for G to pick up phone from last 42min",
                             "F is waiting for G to pick up phone from last min",
                             "F is waiting for G to pick up phone from last -12 min",
                             "F is waiting for G to pick up phone from last 0 min",
                             "G will speak to F later"}

'   Join array of lines into a single string
'   each line separated by /r/n (standard vb line break)
'   (will also work on each single sentence without joining)
Dim input As String = String.Join(vbCrLf, sentences)

Dim pattern As String = "(?<LeftPart>^[^\d\r\n]+?)(?<SpacesBetween> +)(?<RightPart>((([6789])|(\d{2,}))min\r?$)|(now\r?$))"


Dim rx As New Regex(pattern, RegexOptions.IgnoreCase Or RegexOptions.Multiline)
Dim matches As MatchCollection = rx.Matches(input)

For Each m As Match In matches
        MessageBox.Show(String.Format("{1}{0}{2}{0}{3}", vbNewLine,
                                                m.Value,
                                                m.Groups("LeftPart"),
                                                m.Groups("RightPart")))

Next
So from the following set:

A is on phone from last 5min
B is on phone with A from last 7min
D is ready to talk to C now
D is 1min closer to talk to C now
E is waiting for D forever
F is waiting for G to pick up phone from last -12min
F is waiting for G to pick up phone from last 42min
F is waiting for G to pick up phone from last min
F is waiting for G to pick up phone from last -12 min
F is waiting for G to pick up phone from last 0 min
G will speak to F later

the code matches:

B is on phone with A from last 7min
D is ready to talk to C now
F is waiting for G to pick up phone from last 42min


I'd be interested to know what the experts come up with.