May I just say (former KS2 primary teacher here) that I think it's wonderful that you're doing this journal with her, and that she's interested and motivated enough to sit and fill it in every night. Well done you and well done her. It's going to help enormously.
My summer-born son is in Reception, and I'd say he's at about the same stage as your daughter in writing now. He's slightly below expecations in writing at the moment, but the teacher says he will be meeting them by the sumer holidays, so I would say that if your daughter is at a similar stage but a year ahead then she probably does need a little bit of intervention at school. I wouldn't be panicking or anything - kids all develop at different ages and there is PLENTY of time for her to catch up - but all the same, if there's a bit of a gap identified then it's best to start supporting her to catch up as soon as possible.
Have the school not said anything to you in parents' evenings about whether or not your daughter is meeting age-related expectations? What did her report say at the end of last year?
If her vocabulary is good and she's very articulate (this is the same for my son too!) then that's fantastic because once her writing skills catch up with her speaking skills, there will be no stopping her!
Keep building in writing opportunities - you are doing such a good job that already, and if she's keen then that's great. I recently got my son a little exercise book like a school one, with the pages half lined and half blank (you can get them on Amazon) and have told him it's his 'special story writing book'. He has written two mini stories in there already - mostly decodable! Maybe she might like something like that? Or get her a really special book with a glittery cover from The Works or something - anything that's going to inspire her to write.
Other than that, it's asking her to write birthday cards to her friends and to family, sending little notes to grandparents or to cousins or friends in the post (little kids love posting stuff, don't they?!), helping you write the shopping list each week - purposeful writing tasks where the writing is doing a job that they can see the point of.
She'll be fine! But you're right to contact school about it. They need to be clear with you whether she is or isn't meeting expectations, and if she isn't, they should be putting plans in place to help.