Hendrix died in his sleep after choking on his own vomit, and Etchingham says she's often wondered if things would have been different if she had taken him up on his drinks invitation, reported BBC online.
"I thought that if I'd gone round, maybe it wouldn't have happened... I wish that I'd gone round, but I didn't and that's all there is to it," Etchingham said.
The Brit met Hendrix at a 1966 gig in London when she was only 20 and they embarked on a whirlwind romance.
The couple split in 1969 after the star began dabbling in drugs while on the road.
"He started to look really rough. His hair was breaking off, he didn't have healthy skin, he looked as if he'd aged 10 years in two and a half," Etchingham said.
She said she received a panicked phone call from a member of Hendrix's entourage in the summer of 1970 saying the star was having a meltdown in his hotel room and was in need of her help.
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"Everybody was frightened to go in, but I walked in and he was fine with me. He said he had a terrible cold. I got a flannel and wiped his forehead. I didn't know what was wrong so I made sure he was comfortable in bed and left," she said.
Etchingham saw Hendrix for the last time a few weeks later on 17 September, 1970.
"I bumped into him in Kensington antique market. He was buying belts or scarves. And he... Invited me over to his hotel. I said I might - but that was it. I never saw him again. The next morning he was dead," she added.