I don't think they have no chance of happiness in the future. Are you saying they haven't? Sorry, am a bit lost in frustration.
No.
I think you're presenting a overly "glass half full" view that is as unwarranted as a supposition that they will spend the rest of their lives in the gutter.
Their lives are over. In the sense that the lives they had, poof, gone. This cannot be undone. Whatever their new lives look like (be they good, bad or indifferent) ten, twenty years down the line, the chances of the journey and the the destination closely resembling what they and their families had hoped for, are slim.
There is good cause for a healthy degree pessimism that they will not have access to the work, education, social opportunities that would have been open to them. Particularly with the additional complication that their crime is one that attracts a particular degree of moral outrage.
Unlike the bulk of domestic detainees, there is a high chance they'll have a fairly longterm lack of anonymity, because of sustained press interest.
That doesn't mean they have no chance of happiness, even if their lives end up looking nothing like they expected. If they, via luck and judgement, can get past the odds stacked against them. But the stacked odds are there. They are considerable. They don't have every chance as you stated of turning things around. They have a restricted degree of chance. And it is a chance that they have only limited control over making the most of, because it is so highly dependant on the good will of others.
SG's "on paper" come back (because it doesn't really illustrate what her life in the fuller sense looks like) is always the one mentioned simply because there is a paucity of ready examples to point to.
And she had an advantage over these two. Where you have the label "drug smuggler" stuck to your name and face, barriers are created. It requires people to give second chances. And the more people are willing to do that, the more barriers can be lowered or have "wriggle room" bored into them.
Sandra was carrying under 100g, not kilos in double digits.
It's not an amount that people (who are prepared to bring a shades of grey mindset to the table) associate with the sort of commercial dealing that has the capacity to harm and destroy a great deal of lives in their society. Under a hundred grams leaves room to see her as "drug smuggler" more in legal terms than intent. Which increases the prospects of a pass and a second chance. I'm don't think there is any certainty that Oxford would have offered the place had the amount have been measured in double digit kilos rather than double digit grams.
And she held her hands up. She didn't generate the sort of backlash you see when people attribute the "barefaced liar" label to the drug smuggler sticker. Honesty in the face of massive adversity, repentance and remorse have an attractive quality. And tend to go down better with the key holders of second chances than what is increasingly perceived as excuses, tall stories and a reluctance to take personal responsibility.
It doesn't really matter if the 2 in Peru are telling the truth, the whole truth and nothing but the truth. Their explanation is so wildly out of whack with the drug smuggling trade's playbook that they are likely to generate far greater numbers of people seeing them as barefaced liars than even your more typical "I didn't know, I didn't do it, They made me" detainee.
If that explanation it the one proffered long term, including post release, I think it will be even more detrimental to their longer term prospects than it is likely to be to their lighter sentencing chances.