I believe his point was that with others the rate of grief per unit time was ineffective compared to farming grief seeds as indicated by Kyubey. While during a timestop no time passes so the rate of grief gathering approaches infinite from the objective temporal reference frame.Sabrina+anyone=Unlimited Magic Works plus constant grief attacks. We are essentially a walking pile of Grief Seeds and that's without actually using our own powers.
If she's trying to assemble a team in opposition to her...that's still dumb, but more sane.
As to assembling a team my thought was that she might believe, correctly, that our side would be unwilling to have people contract if we can at all avoid it. While there's still a need to have a team of magical girls to engage Walpurgisnight. Thus she could cause girls to contract and foist them off on us so we can maintain them to battle the upcoming Walpurgisnight. A lot probability scenario, but at least fairly reasonable if her goal is simply to survive.