I sympathise but the grounding and no phone is far too long. Way, way waaaay too long.
A teenager without a phone is a very unhappy teenager. And that is a hugely long grounding.
When my boy does something I ask him to tell me his perspective and ask him what he thinks would be an appropriate consequence. Usually it is exactly what I had in mind so I can say, I think that sounds fair. Then he has buy-in to the consequence rather than just fighting it. My older one was almost the same though the consequences she dreamed up were much more severe than I had in mind 😂
The thing with teenagers is that developmentally they are designed to resist and move away from family. The difficulty is in allowing them to do so while maintaining boundaries.
I know your daughter has made some terrible choices but it’s very important not to go sergeant major on her.
Frienda are everything to a 14yo, she must feel very unhappy not being able to see or talk to her friends for such a long time.
I say this with every kindness, have you considered doing a course for parenting teens? I would also get therapy - for you and her dad, not her. You will get someone to hear you out, and guide you to make considered decisions. It will help to reduce the conflict in the home.
Don’t isolate her as the problem, it’s a family issue that has to be resolved with everyone on the same side.
I tell my kids, hey the teenage years are tricky. Without a doubt you’ll mess up and so will I, but let’s keep talking and try to work things out.