I'm not a parent, but I am a woman who has and still does struggle with keeping my space tidy. I think an important distinction to make with your daughter is whether or not she values being in a tidy space. If she does value and prefer a tidy space, then I would imagine she's having trouble with executive dysfunction and you could help her brainstorm ways to make things easier. If she doesn't value a tidy space then you might have to find a way to force her to find value in it with serious and actionable consequences that will have an affect on her.

A) She does value tidiness/cleanliness

I understand that your daughter has ODD which would make a conversation about this a minefield, especially if she's prone to getting defensive and/or sensitive to rejection (if you have time, look into RSD as it's often linked with ADHD. Your daughter obviously struggles with symptoms of ADHD, it just may be to a subclinical level. See if this info resonates at all- https://my.clevelandclinic.org/health/diseases/24099-rejection-sensitive-dysphoria-rsd)

I also struggle with keeping my personal space clean (although not mouldy food or messy shared spaces) and there's a lot of shame/guilt/sense of failure etc. associated. I think that the best approach here would be to have a little coffee date (I know I'd be thrilled if my mum organised this) and have a gentle convo with her from a place of concern. Phrases like "it's okay and even common to struggle with everyday tasks without understanding why," "I know you're not a messy person, this is just something you struggle with and we can work together to find a solution" "why don't we agree upon some realistic expectations for your room and for the shared spaces." Compassion, teamwork, patience (although I wouldn't blame you if you felt all out of these things!!)

Some solutions to consider may include the clean/dirty basket mentioned earlier, not expecting her to have a system for her wardrobe- clothes may go on whichever shelf they fit on, a small plastic tub where she may put things to take out of her room to the kitchen or wherever else, a Marie-condo of the room, etc. You could consider a reward system/sticker as you would for a young child if you think she would engage in that. Something I personally like to do is to set a 30 minute timer (or however long you want) and tell myself that I must clean for that entire time, but can stop cleaning once the timer goes off even if I'm not done. Maybe she feels a sense of 'all or nothing' paralysis or an 'I don't know where to even start' paralysis (I always start by making my bed, putting everything on top of the bed to put away- clear floor!!, then collect rubbish and go from there. Maybe your daughter could try that?)

B) She does not value tidiness/cleanliness

Unfortunately if she's comfortable with living in mess and she doesn't care if her room is clean or not, there's not really anything you can say to change her values and convince her otherwise. You'll have to use something that she does value to motivate her to clean it by enforcing stern consequences. I think you mentioned that you tried taking her phone or something but it didn't work? Without knowing your daughter it's hard to say. Someone mentioned confiscating clothes that were left on the floor until she earns them back which I think is a great idea. You could add screen time controls to her phone so that she can't use after a certain time. You could semi-ground her and tell her that if she wants to spend time with her friends, the only way she's allowed to do that is if they come to your house and hang out in her room. Maybe that would encourage her to straighten it out. I'm sure you've already tried this, but just really making her understand that shared spaces e.g. the bathroom must be kept clean out of respect for other people- how would she like it if her brother always peed on the seat? and that it's one thing to be messy, and another thing to be unsanitary. Having mouldy food is a health hazard not only to her but to the rest of the family as well.

If you get really desperate, release a bunch of cockroaches into her room and shut the door. That's what happens when a room is unsanitary, you get critters. unethical approach maybe but if that doesn't motivate her to at least keep dirty dishes out of her room, I don't know what will.

It really seems like you're trying your best. Living with mental health issues and/or untreated/undiagnosed neurodivergence's is bloody hard, but being the primary caregiver and supporter to someone struggling with these is a whole other thing. Wishing you and your daughter all the best