Black top, white collar

[QueenMabby]

My DD has a black jumper with a white lacy collar. It's her pride and joy. I've put it in a woollens wash with some other jumpers. Used a colour catcher just in case but one of the jumpers has obviously run a bit because now the white collar is various shades of light pink.

How can I fix this? I can't bleach the collar because it's attached to the black jumper. Any advice?
Thanks.

Bump. Anyone?

Try washing again with another colour catcher?

Habe done that. No joy.

I do not buy t shirts of jumpers like this, as I hate the thought of laundering them!

Can you use a cloth soaked in a vanish/napisan solution to spot remove the strain? You could put the jumper in a plastic bag with the collar poking out a hole to hopefully protect the rest of the fabric?

How is it constructed, can you remove, treat then reattach the collar?