Be blunt - "SD, do you like it when people spit their food all over you? No? Nor do I, that's why you should never speak with your mouth full. "

Do it back to her and show her how rediculous she looks?

I think you need to maybe try the remind.. remind.. remove technique with her.

First time in a meal she does it.. "SD, please finish chewing and swallowing before you speak.  That is not good manners"

Second Time  "SD, For the second time, do not speak with your mouth full.. if you do it again.. you can take your plate to the kitchen to finish eating by yourself".

Third time  "SD, I asked you nicely twice.... please go finish your dinner in the kitchen.

I am hoping if her dad is at the table.. he would speak up.. and remind her one of those two times.. but if it's just you two.. then you can try that.

When she is repeatedly deprived of her captive audience for her stories.. she may eventually learn to self regulate.. and perhaps only need the occasional reminder.

Hand her  a napkin and tell her to spit her food out before she talks to you.  She doesn't remember to chew and swallow so maybe spitting it out would teach her.  You could also just ban her from talking to you when you all are eating.   I remember when my bios were toddlers and doing this kind of stuff , especially the whining.   I just told them flat out I didn't understand them and would not respond any differently until they spoke normally.  I might pull that trick out for this.  I mean you do have to teach her how you work.  I'm surprised you lasted this long , I would have lost my $#it a long time ago. 

My YSD was like this - completely. I did the constant instruction of "Please close your mouth when eating, it's gross to see and hear it." Over and over every single time - multiple times. DH actually did back me up on this one. If not, I would have personally left the table.

YSD also developed this very weird habit of "lip smacking" when she was eating, around age 12/13. Oh, that was the most annoying thing. I asked her repeatedely, "Are you ok? You are doing a wierd smacking noise." Eventually that stopped too.

So far, ate 16.5, and all that's done and gone.

So my SD16 has had adhd since she was 10ish? Routine and repetition is essential.  She will get frustrated and angry after the 10th time you tell her during one meal, but explain that this is to help her remember-not to be mean.  We still have to use this method with multiple things to this day...it's taxing.

Every meal. Literally like not just dabbling he does not use a fork unless absolutely necessary. I've watched him eat a fried egg and many other things with his FINGERS! It's so gross. Many excuses are made "he's spent so much time in the wilderness blah blah blah " well not in the seven years I've known him!!! He's also said things like "the viking in me" uh huh.......so I'm no help. I can tolerate it if I'm only around it once a month. With the new weekly meal schedule I just excuse myself or suggest DH take him out. 

Tell her she will not eat again until the next meal and if she does it again, she will keep losing her plate until she learns not speak with food in her mouth.

Hunger is s great teaching tool.

Lather, rinse, repeat.