I'm sorry you are going through this. Of course I can't know for sure but it sounds like methadone (weight gain, nodding off, confusion.) But could be any opiate. Or benzos (valium, xanax) Or a combination. Doesn't really matter. The point is that is those are drug using symptoms.
What you can do long distance is make sure you give her zero money. You can also let her know, lovingly, that despite her protests, you believe she is using drugs and she is not invited back until she gets help. No fights, no threats, no manipulation. Just let her know.
In the meantime, I strongly suggest alanon. There are so so many parents, spouses etc.who have a drug addict loved one and they are at their wits end. Alanon is where you meet like minded people and you'll learn tons of tools on how to be calm and have peace despite the addict's behavior.
Others will be chiming in too:)
Hello LMB Welcome to the forum. I'm sorry that you find yourself in this situation with your Daughter. She needs rehab. If you are financial supporting your Daughter you need to cut off any funds as Jifmoc said for every dollar you give a addict it goes to furthering their addiction every-time you send money for food gas it is furthering her addiction. Cutting off funds will force her to see her situation better for once you run out of options for scoring you begin to face reality. Firm for she will cry beg scream but you need to hold strong She needs to hit her bottom in order to want to get clean.. I hope I have been at least a lil helpful Do not support her habit for it will lead to her death. Heroin is no joke it is a powerful drug that is cut with who knows what so today stop the money ok. I wish you all well. lesa