Hi Lucy,
Happy New Year! Sorry poor Candy is having a flare up. Here's probably way too much information about how I dealt with Marshmallow's IBD.
I got the capsules from Whole Foods ($10). Then I'd split open a capsule, mix half the contents with a teaspoon of warm water, and stir until it thickened. If it turns into a thick paste, add more water. Then I'd spoon it into a syringe and give it to Marshmallow that way. She was fine with the taste. She wouldn't eat wet food, otherwise I might have mixed it into food.
I've also read what Mogs said, that you want to give it an hour or two away from meds so it doesn't interfere with the absorption. I also read somewhere that you don't want to give it at the same time as food since it might inhibit the absorption of nutrients, but I've also read about people mixing it into food so there seem to be conflicting ideas on mixing it with food.
It didn't raise her BG at all. It also has a little fiber in it, which is good for IBD kitties since they often have diarrhea or constipation. Here is a site you might not have seen that discuss SEB. IBD Kitties (and their Facebook page) are strong proponents of SEB and that's where I learned about it.
http://www.littlebigcat.com/health/slippery-elm/
Are you giving her digestive enzymes or probiotics on a regular basis? Marshmallow benefited from the enzymes as soon as I started giving them to her. Her fur got softer and more glossy within two days of me giving them to her. I was going to start her on probiotics but then she crossed the bridge. Here are the enzymes I got for her (recommended on the IBD Facebook page):
http://www.amazon.com/Animal-Essent...ment/dp/B0002ADJYM/?tag=felinediabetesfdmb-20
I bought these on chewy.com for about $10 and gave Marsh 1/8 tsp twice a day. You can mix them into the food and I think they must be tasteless. I mixed it into Marsh's pumpkin and syringed it.
About digestive enzymes: These help kitty digest the food so they use more of the nutrients in the food. Start small, and work up to the recommended daily dose on the bottle (best if divided into however many meals you feed and added to the food at each meal time). You will want to make sure none of the ingredients bother her, so start with digestive enzymes and after kitty is up to the full dose and tolerating it well, then maybe add probiotics. You will know if kitty is tolerating it if there is no vomiting, no mucous in the stool, or anything else that indicates it’s upsetting kitty’s system. If she tolerates and does well on those -- and you should know inside of two weeks -- you should see smaller stool, slightly harder, but not constipated. Less volume of stool means she’s using more of the nutrients in it.
For more info on probiotics and IBD kitties:
http://www.ibdkitties.net/Probiotics.html
I bought Renew Life Life Ultimate Flora (15 billion CFU), and was going to give her 1/2 capsule, twice daily. It has lactobacillus and bifidobacterium. Marshmallow alternated between constipation and diarrhea, which indicates a tug-of-war between issues in the intestines and issues in the colon, so theoretically that combo would have helped her.
That's probably WAY too much info. Feel free to tag me if you have IBD questions since I did a ton of research on it and tried a variety of things on Marshmallow.

Good luck!
Shane