Hi Kirsten,
First things first, you haven't screwed anything up. She's quite young still and barring any underlying issues like reflux, etc, it should be pretty easy to get her back on track. I know it doesn't sound like fun, but it's much easier (and will take less time) to start to resettle her now than when she gets older.
With regards to the DF, is it something you want to do? It doesn't work for all babies, but you did have a couple good nights with it, so you may want to keep at it. I think you have a couple options. If you choose to keep the DF, keep it for two weeks before you reassess. Do the DF and then try to resettle at the first NW. I think at 9 weeks, you could try to resettle anything under 4-5 hrs. At this age, I actually only tried resettling for 15 min before I just fed. Does she fall to sleep independently? Do you use shh/pat or some variation to help her settle? Use that same thing for NWs and she should settle pretty easily. If she doesn't, pick her up and try to burp her, she may be uncomfortable. If she burps, put her back down and settle her. If she doesn't, you can try resettling again or if she's rooting just feed her. The other option would be to drop the DF, feed at the first NW because you'll be pretty sure she's hungry and then expect one more NF. If she wakes within 2-3 hr of the first feed, resettle her as I've mentioned already.
The only way to break the habit of bringing her into bed is to not do it.
Work at resettling her the same way you put her down during the day and at bedtime. If you're very consistent with it, she'll start to respond easily. I don't think co-sleeping is bad in and of itself. Lots of people bring baby into bed after the first NW, but I'd be hesitant to let her sleep on the Boppy as it's a much higher SIDS risk.
If you think she might be waking at 2ish due to gas, do you burp her at the DF? Mine always needed a burp at every NF, including the DF to sleep soundly afterward. They're so relaxed after feeding in the night, it's usually pretty easy to get it to come up. Otherwise, you can do as I suggested before and pick her up and try to burp her then and then resettle. I'd opt for getting them out right after the feed, though.
One last thing. You mentioned you're back to work. Did this happen during the whole GS, two week stretch deal? Often babies will start waking more at night when there's a change like that, whether its due to just the change in routine or to get more snuggles in with mom. I always think its the latter.
So, it could be just a matter of waiting for her to settle into this new way of life.
Oops, I guess that wasn't it. Would you also post her EASY for us to take a look at? It could be that there's something as simple as a tweak to help things out as well.
Sorry for the super long post, I guess I'm long-winded tonight.