Its good that you will take her to the vet just to rule out uti. She is young and may hide the symptoms well so its best to rule it out. FWIW it sounds like you are doing a great job with her and that she has come a long way. Sorry this is happening at a time when you have so much going on!
Usually submissive or excitement urination happens with human interaction more than with other dogs. You can try talking to her in a lower voice ( high excited kid voices and baby talk usually make it worse), try petting her under the chin/throat area rather than on top of her head. Don't hug her or grab her, even playfully. Try to be calm and reassuring. Try it for a couple of days and see if it changes anything. If you notice a difference ask the vet for some tips on submissive or excitement urination. I was in the veterinary field for a long time, but I've been out of it for a while now so my info could be out dated.