I've posted before about my unpleasant first experience. Luckily, I persevered, and quite enjoy it - can't get enough.
However, I'm sure some women do not like the taste (along with other possible reasons above). I understand some women spit. (What is the etiquette on that? Does the man pull out a hanky for the woman? Does she keep a spittoon handy?)
As has been posted, ask her! You can't resolve any possible issues, unless you know what that issue is. Of course, if she simply doesn't like it, she just doesn't like it.