The Greens have decided to step back pending their autumn conference where they will make a decision on whether to engage fully with Yes Scotland.
Co-leader Patrick Harvie appeared at the launch a fortnight ago, but has since criticised the campaign for the way the SNP were controlling "every key decision".
Ms MacDonald, while having some sympathy with that view, believes it is all the more important to work to keep the bandwagon on the road.
"I have offered to work as an honest broker between people who have so far not got together," said the independent MSP for the Lothians.
She said she could help because she was outside the campaign, everyone knew where she was coming from, adding: "Over the summer there should be a period of silence on the part of the SNP high command until they have put in place what they should have put in place at the outset."
Meanwhile, Colin Fox, convener of the Scottish Socialist Party, said their experience was different to that of the Greens.
He said: "As far as we are concerned we are fully part of the Yes campaign, and my attitude is that it has been a success."