Angela I am so sorry for your loss. It is always so hard to lose a loved animal.
If you are seeing a lot of worms in the poop then the recommended plan of attack is to use piperazine first, followed by albendazole 10 days later. The logic behind this is that piperazine only gets the roundworms, whereas albendazole targets a whole range of worms. If a chicken has a very large worm load then paralysing them all in one go can either lead to a toxic overload from the poisons they produce when they die, or a blockage in the gut caused by a whole mass of paralysed / dead worms that the bird is unable to expel. (All of this is stuff I've learned from @Dawg53 - the resident BYC worming expert!)
I suppose that if you wormed with albendazole and she had a large worm load then it is possible that this caused her problems, although without a necropsy it will be impossible for you to know for sure. Don't be too hard on yourself about things. Even if this was the cause, you weren't to know. We all make mistakes with our flocks whilst thinking that we are acting in their best interest - the only thing you can do after something like that is treat it as a learning curve and try to make sure that you don't make the same mistake again.
The worming routine that I've found online is as follows:
Day 1 (roundworm only) Wazine (piperazine) 80-100mg/kg bodyweight
Days 11 - 18 (all main worm types) Valbazen (albendazole) 1.43mg/kg or flubendazole 6mg/kg daily for 7 days (no egg withdrawal required with either of these) or Safeguard / Panacur (fenbendazole) which requires a 7 day egg withdrawal.
I have wormed chicks aged 8 weeks and upwards using this method - just making certain that I weigh them in advance and stick to the mg/kg bodyweight dosage; I don't know if it's recommended or not, but so far they have all survived!
