You can't, and shouldn't even try to hide a significant chronic condition like this from someone you are considering spending the rest of your life with. No need to tell everybody you meet, as soon as you meet them, but if you are in a committed relationship it would be a good idea to mention it sooner rather than later. If you wait too long she might be upset that you didn't trust her enough to confide in her. And, if she feels like she can't handle being with you, it would be best to know that before you commit too much to her emotionally. (That would be really dumb/panicky on her part, but unfortunately this happens sometimes.) Most mature adults know that nobody is perfect - we all have issues/baggage of some kind - so don't let your self esteem get so low that it allows you to think you should forego taking a shot at happiness "for her own good." Let HER decide what's good for HER, don't presume you can make that choice for someone else.
Jen, 42, happy partner of James and Moma to Evan, 14, & Lucy, 12.5 (Crohn's dx @ age 3; on Remicade since April 2010.) I take piroxicam, Flexeril, & Nucynta ER nightly. 3 anti-TNFs didn't pan out for me.
"Science is the father of knowledge, but opinion breeds ignorance." -- Hippocrates