I have to agree with all the comments about the music on the soundtrack being really annoying, but, for what it's worth, I believe that the woman singing may be an uncredited Buffy Sainte-Marie, the well known Native American (First Nations-Canadian) folk singer from the '60s and '70s.
"That mans' nuts!!! Grab 'em!"
She's only credited as "Sybil" on the OST album but more likely she's actually Susan Duncan Smith which co-wrote the lyrics.
shareThanks for the info. However, the fact that she's credited only as "Sybil", but is more likely actually Susan Duncan Smith suggests to me that it may be Ms. Saint-Marie recording under an alias.
"That mans' nuts!!! Grab 'em!"
I doubt it's her, Buffy's voice sounds sharper and uses much more vibrato but it's not impossible.
More likely the singer might have been inspired by her since Buffy sang on the soundtrack of the similarly-themed Soldier Blue few years earlier.
Mistery solved! The singer's full name is actually Sibyl Amarilli Mostert, a Zimbabwe-born Italian singer, she made a brief attempt at a pop career in the 80s under the name 'Sibilla'.
Here's one of her rare TV appearances: https://www.youtube.com/watch?v=ubYKQOJnNPI