If the requisite amount of dough is made that would require taking challah if it were baked in the oven, should one take off challah with a bracha if she intends to deep fry the dough instead?
No, one should not recite a bracha. The Shulchan Aruch (YD 329:3) rules that thick dough kneaded to be boiled (which is what deep frying is) is exempt from Challah. The Shach notes that some opinions don't care what his intentions are when kneading, and if it is a thick bread-like dough it is obligated in Challah from the time of kneading. The Pitchei Teshuva there also notes a possible opinion of Rabbeinu Tam who argues on the Shulchan Aruch. Thus both recommend separating Challah anyway out of doubt, but to refrain from saying the bracha.
Take a look at challah 1.4 -1.5. A deep fried dough is not lechem I.e. a bread product. The Torah only obligates bread products in the chiyuv of challah however the chiyuv of challah takes effect at N earlier stage - during the kneading process. So there is a machlokes between rabeinu tam (sefer hayashar and pesachim (38b) )and rash on the type of dough. Rabeinu tam holds that kneading effects effects a chiyuv chalah and as soon as the obligation is effective it cannot be released so in order for such a dough to be exempt it must be a batter( batters are not kneaded) and deep fried thus there was never a point during the baking process that a chiyuv was effective. The rash holds that you can even knead a dough and this will dough will remain exempt providing that when you are kneading this dough you intend to bake into a non challah liable item. The rash holds in hilchos chalah that any time you intend (during the kneading process)to make a dough into a non chalah liable item the chiyuv will not be efective although the dough is kneaded.