Is she sick? Allergic? Have you changed the way you cook or what you cook? More or less spicy? New foods? Keep in mind that children's tastes change, sometimes often, and sometimes when they say something doesn't taste good, what they mean is it doesn't feel good, as in texture. Some kids are extremely sensitive to texture and this sensitivity can seemingly appear overnight. Experiment with the food you're serving to see if you can tease any of this out.
If none of these possibilities seem to be the culprit, I would consider this is an attention-getting devise. You mention she's never had eating issue before and my guess is that the first time it happened, it was genuine; she didn't like something about what was in her mouth. It got her a bunch of unexpected attention and now she's experimenting with the attention: If I do it again, what does mom do? What about tonight? Follow the rule of thumb that the less attention you give this behavior, the faster it will disappear. If she's been a good eater, she will at some point decide she misses the food. She'll decide that sooner if the behavior not only leaves her hungry, but also doesn't get a reaction from you.
That means you have to stop worrying about what she's eating. It's easier to do this if you think about her diet over the course of a week rather than from meal to meal, or even day to day. It surprises most parents to hear that children typically get the nutrition they need in the course of a week, assuming, of course, that you are putting appropriate food in front of them.
Here are some suggestions:
In addition to making sure there is healthy food at every meal, be sure there is something she likes to eat.
Keep portions small & appropriate to what she will eat so that if she does eat something, she feels successful about it: "I ate that!"
Make this about manners, not about eating. Have a family rule about chewing: "If you don't like something, the rule is to spit it out into a napkin." Show her how to do this politely. Let everyone in the family practice, so it's not just aimed at her. Couple it with another meal-time rule, as a kind of refresher for everyone. All of us no and then find something so distasteful that we want to spit it out, right? By teaching her how to do that, you just might remove the attention-getting "fun" from it and it will lose its appeal.
When she starts to gag or over-chew, be matter of fact, hand her the napkin and remind her, "Remember the rule?"
Make the meal pleasant, and a family event. Engage her in conversation.
Avoid punishing her. That makes mealtime unpleasant, which leaves a nasty taste in everyone's mouth.