I agree with you ... i do not associate anal with bdsm out of my 5 "nilla" girlfriends, only one had not tried it. Now enemas ..well i have not spoken of this but i would be surprised if any of them had tried one.
I too have difficulties with reactions to lube and, not to sound all crude, i have found the best lube is good old fashioned spit ... i am not sure why no one ever recommends this but i find it very effective.
i found the most "comfortable" way of trying anal initially is to lay her flat on her tummy and yes go slow and watch her body for cues to go harder.
Good luck and have fun!!