D.K.
I am laughing, not at you, maybe with you.
I do after school child care, most of the kids I watch are around nine. Your daughter is normal, promise.
Kids are developing and hitting weird stages with their brains and bodies. I don't think it is lack of common sense as much as just not thinking. She is preoccupied in her brain right now. Not that it is okay but she needs to be more aware of what she is doing. That takes practice.. Don't compare her with the 10 year old as it is rare that they are really mature at that age and birth order can have something to do with that!
Post up a chart. For every infraction regarding poor judgement, put it up on the chart. When she does something she has done well and thought out well, put it up for her to see. After a week, have her sit down with you and your hubby. Go over the chart. With each bad decision, ask her "well, how could this have been handled differently?", make her use her brain to figure it out. Then discuss what responsibility and accountability is and why it is so important. If the bad decisions outweigh the good ones, tell her for every week it continues it is a month off the cellphone, meaning adding a month to not getting one. So say just for what you listed that is four months out on the cellphone. It should be earned with good judgement but there is nothing wrong with her.
I don't think a 9 year old is needing a cellphone anyway. I think once kids are in midhigh, walking alone to and from school or doing more social things out with friends, cellphones with restrictions make sense. That is my two cents on that. You said yourself that the oldest is more mature and has a father with visitation and that is your reasonings.
I have friends that try hard to keep things "fair" amongst her kids and it is ridiculous as a 6 year old getting the same gifts as a 9 and 12 year old because it seems fair to spread it across the board! The bottom line is some kids aren't ready for the things the older ones are at the same age. It isn't possible nor logical to me to worry about being fair with age as much as actions speaking louder then words and she needs to prove it to you.
Hugs, she is normal! Puberty makes their brains goofy! :)
Consider yourself blessed to have a 10 year old with common sense and don't compare, that will build resentment with the girls. Good luck.