This is an online vets advice
Rabbits can ingest paper and wood without problems as long as they don't get too much in the system at one time. The beneficial bacteria in their guts that allows them to get nutrition from hay can also digest the cellulose in twigs and paper, as long as the system doesn't get overwhelmed with volume and cause a blockage.
My rule of thumb is that if a toilet paper roll disappears in less than a week (for an average to large size rabbit), that's too much. For a dwarf I would say two weeks. Since wood is harder and takes more time to chew off bits, it would be pretty difficult for her to eat too much too fast of that.
If she's going through the cardboard too fast, you can of course give her smaller pieces and let a couple of days go by between new pieces. Also, try getting thicker, harder cardboard such as the rolls that come in plastic wrap, or salt canisters. Sometimes you can find small pieces of cardboard concrete forms at home improvement stores that are really thick and hard. She can chew on those but will be hard-pressed to eat them up quickly.
Another approach is to eliminate the "edible" toys for a week or to and increase her hay ration. If she gets used to eating lots of hay rather than chewing cardboard, perhaps you can introduce the regular cardboard toys back to her and she won't be so apt to ingest them when she's full of nice healthy grass hay.
Thanks for being concerned for your companion's wellbeing. If you haven't yet discovered it, the site
www.rabbit.org is a wealth of info on all things house rabbit, including FAQs on toys, chewing, and diet.