You've probably already thought of this but just in case...
Limiting her liquids for at least an hour or so before meals and then offering just a SMALL sip after each bite will definately encourage swallowing since it's hard for a little one to hold food in their mouth while swallowing a drink. If choking is a concern, the drink could be offered after she shows you her empty mouth.
If she's old enough to understand the concept, a timer or hour glass could be set at the beginning of meals to show how long before desert/fruit/treats will be served. Make sure you allow enough time so that she doesn't have to rush too much. When the timer goes off, the table is cleared and the treat is served to those who are done eating. Left overs are immediately put away and the kitchen is "closed" untill the next meal. Explain that this is not a punishment, but rather a neccesity since you can't get on to other things if you have to spend hours manning the kitchen. You may encounter some crying, pleading and requests for a second chance at first - but if you hold your ground that should quickly subside.
If you're out and about at meal time and maybe running through McDonalds, you wont be able to use the "closed kitchen" explaination. So if she likes gum and is old enough to have it, a piece after meals will encourage a final swallow.
Keep in mind that some people are just slow eaters. Others are "grazers". Myself included. I'm generally full after only a few bites. I sit with everyone untill they're done then usually put my plate in the microwave - knowing I'll be hungry again in an hour or two and not wanting to pull everything back out of the fridge. Is it possible that your daughter is losing interest in swallowing because she's full?
I think that the biggest thing to keep in mind is that it probably isn't really a long term problem and you may not even want to address it unless it's creating other issues for you (like being on time to after meal events). Most likely, she'll just out grow it. When she starts school, she'll quickly realize that she can't chat with the other kids if she's holding food in her mouth. For now, if you have her brush her teeth after meals (or you can use one of those rubber infant brushes if she's really little) tooth decay won't be a concern.
Best of luck to you!
C.