When Is A Lie, The Truth Or The Lie The Lie?

Hello all parents out there, we all are here. That is very sad and unfortunate. I am sorry we all even have to be here.
I am new to this. My 32 y.o. daughter has been on heroin, for at least a year, probably 2. I've known because I had suspicions and snooped. Not hard to find when make up bags have tons of needles, old and new, razors, open pen casings, tiny baggies and foil.... Hardly hidden. By confronting her, it only brought on screaming arguments, telling me she had friends that came by, or the old tenant.. actually I could go on and on.
Finally she is in jail for theft and selling stolen items. Only now in jail, has she admitted. It's been almost a month to get the bail hearing. My question to all, maybe even from one success story: How to know when the addict says they want to change and get help and get out because:
1: They want to get back with their friends/addicts/dealers
2: They want to admit it all, to appease you?
3: They say they know they need help and, do they really want it? Again to appease you?
4: They say all these good things, do they genuinely mean it in their heart, but for that moment only? Are they truly deceiving themselves, believing their own bs?
5: And last, but the best, that they really do and will give it all up, whatever it takes?
How do we know? Yes, we all want, #5 but is it because it is what we want to believe? Is there ever a time when those 10% ers that want to leave their messed up world behind them, when do we know> Is there any real proof, ever? Or are they Heroin addicts for life, even if in 45 yrs they still have never done it again. Just as it's said, once an Alcoholic, always and forever one?

I don't want to hear from friends that have never had children, "she's an addict forever. Just let her end up dead." Has anyone else heard that from girl friends? My other friends, that are Moms, would do anything to help their addicted child, (young or older) Is it cruel, or me being dumb and gullible? Do I give up hope, because she will never become normal again, ever?
Please advise. Can I psychiatrist know the truth? Do we have to do a hair test, blood and urine test, 3x a week for years?
May I gently suggest that she will probably only be serious about stopping when she decides by herself with no conditions and then proceeds to want to do the work it takes (detox, rehab, NA etc. ) to get clean.