Could be Ringlet the Rainbow Curl pony too, but she's not rare either as far as I know. Or Skydancer. (Very common.)
Rainbow Magic (the Rainbow Curl pony) has a white streak first, pink is third. Find it hard to imagine from the description but...
Maybe?
Floater seems the best bet to me too, as from a glance it might look like her mane was a coloured streak with the green streak behind it. Depends on what shade of pink I suppose.
...Would Skydancer's tail look pink overall? Most Rainbow pony tails look kind of greenish?