I would consider pushing a guppy into a babies mouth, but I think that is different to syringing food into them. "Introducing" a guppy you aren't forcing it down, you still rely on the snake to swallow it. Perhaps a bit of fish with lots of skin still attached? I'd even try goldfish if I couldn't get guppies (although not if they had visible worms), one or two wouldn't hurt and if it got her feeding. I think saying "put her down and deal with it" is incredibly unfair, I'd get slapped if said that to Char.

This situation is a bit different to my baby that never ate, if Angel has eaten in the past she's more like our Bethan than an FTT and I'd cry like a baby if I eventually have to euthanise Bethan if her back problem gets worse.

Don't let your love and compassion cloud the objective question that you need to answer every day - "Are my actions helping this animal, or causing it more suffering?" It's something only you can make the call on, and you've got advice and support around here whatever call you make.