Hi there. I would certainly advise that you get this checked out, just in case it's something that needs treatment.
Fluid in this area could be linked to one of several things, and their are lots of vital structures in the throat.
The fluid may be an abscess, cystic fluid, or oedema (fluid under the skin from poor drainage).
The throat contains structures called 'submandibular lymph nodes' which can respond to infection and inflammation and become very large, so they may be involved.
A vet check will decide if she may need a course of antibiotics, or if it's just a lump that needs to be monitored, but it's always best to get these things looked at to be on the safe side.
Andrea
Dog Veterinarian
bvm&s degree, 15 years in companion animal practise