Hey Jac!
I think you have two separate issues with this dragon - just for starters... Before I ask lots of questions, we'll start at the beginning...
Firstly, we'll tackle the "not walking around so much" and the vent - you say she feels "tight"? Run a luke-warm bath for her (I know you said you've done this already, just humour me!), just up to her shoulders, so she can 'swim'... If she's impacted (sounds highly likely), she'll try and poop in the bath fairly quickly. Watch to see if she strains - if she does, gently manipulate by massaging her tummy with your thumbs on her back, forefingers gently massaging her tummy, rolling toward the vent. This needs to be done GENTLY, but with just enough pressure to help her... (I'm guessing she's on sand, or bark or some such?) When she's finished, as quickly as you can, run a fresh bath for her, to relax her. Let her do what she wants, but keep an eye on her vent. If she strained too hard, she may have a prolapse (another situation entirely, let us know if this occurs).
As for the lump on her jaw, it's really too difficult to diagnose without photos. Does the lump hurt her? Does it feel squishy, or hard? If you can post a pic or two of this "lump", that will help us help you to help her...
Now the questions! Could you please explain to us what her enclosure set-up is like? Heating, UVA/B tube brand, how far away it is from the dragon, temps, substrate, furnishings, feeding... Your answers to these questions will give us a 'picture' of the husbandry (not saying that's the issue, but there's obviously something "amiss") and may just pinpoint a reason for certain behaviour...
As for the vet - the soonest appointment may not necessarily be the best - unless it's with a reptile vet... Sadly, veterinarians don't major in herpetology, so some know very little about the animals - to the point it may be hazardous.
Anyway, if you get the manipulation done in the bath, and can get some pics of her jaw up for us, answer these questions, we'll be able to help you a little better!
Good luck!
Best,
Carolyn