Full marks on every grammar worksheet, and none of it shows up when she writes

Class 3. Her English worksheets come back with ticks all the way down: fill in the correct tense, pick the right article, join the sentences with 'and' or 'but'. Then she writes four lines about her weekend and it's 'we goes to the park and we eats corn', with no full stops anywhere. I can see two ways to go. Sit with her writing every evening and correct as she goes, which she hates and which takes the fun out of it. Or leave the writing alone for now and trust it catches up with her reading. Her teacher's only comment so far has been 'good effort'. Has anyone seen this gap close on its own around this age, or did you have to work on it?