Hhmmm... I wonder if the colour scheme will effeminate the mould at all? Look at Binaltech Arcee, I think that was done well in terms of taking a rather masculine mould (Overdrive) then giving it a less masculine looking head (Decepticharge) and then painting it in white and soft pink colours. I thought that worked wonders in effeminating that mould. So maybe the way you work with the colours might help to make the figure look more feminine. You could try to make the colours as pastel as possible. e.g. with the purple go for lilac, lavender, dark fuschia etc. See if you can add the same pastel purple around her mouth to make that "lipstick" effect. The turquoise should go well with the pastel purple. Perhaps the trick is in selecting the right shade of purple and getting the head/face to look more effeminate. It would take the focus away from the body proportions.

I just Googled Transformers Slipstream and found some other custom figures people have made.
Animated Slipstream
TF Prime Slipstream
Beast Hunters Slipstream

And here's a piece of fan art for Masterpiece Slipstream.