One thing to consider is that DITHOR books should be below their "instructional" reading level. They should be easier than the books that stretch their reading level as you want them to be able to analyze characters, setting, plot, etc. and the other story elements rather than spending their time decoding and deciphering the meaning behind the words.
I understand wanting to push ahead. My 11yo DD just caught on to reading this year, too. We had her tested last year for LDs (came back as negative) but her reading level (age 10, finishing grade 5) was at grade 2.7! This year we dropped all LA in favour of doing Dianne Craft's Brain Training for 6 months (then added grammar, dictation, etc. back in) and, started piano lessons. She also got tubes in her ears (she was suffering from ringing in her ears for over a year) and a change in glasses prescription. I don't know what was the magic bullet (any or all of the above) or if she just needed time, but she, too, is finishing the last Level 2 book now and choosing to read her own books outside of school time as well. Yay!
I was planning for her to do Level 3 books over the summer and into the fall just for reading (using a similar to DITHOR schedule for pages/day) without actually doing DITHOR. She's using another reading program for comprehension and story elements that is more independent, since I'm running 4 guides (5 next year) and plan for her to start DITHOR again when she's done this year of that program (about 15 % into it now and will work on it through the summer). However, I'm reconsidering as I discuss it here in type, and I think I'll continue her reading (our library has a summer reading program) through the summer but save Level 3 books for her to use for DITHOR when we're ready for that - by then she'll be above that reading level instructionally (I hope

) and so they'll be a good fit for DITHOR. It is pretty easy to skip a level in the upper levels of DITHOR (for example, go from 4/5 to 6/7, skipping 5/6, or doing some books from each one) but I don't want to push her too hard right now as she's just gaining confidence (as much as I would love for her to be at grade level!).
Although enjoyment of the books is important, it would be better (IMO) to pick alternate books from the Book Idea List at the right level than to move up prematurely. I think the last thing these late readers need is discouragement in their new-found skill.
Looking forward to hearing your feed back and others' responses.
Blessings,