Yupp, Pretty girl! Black and Tan.
She may be fearful of the dominant dog and thus lunging to attack and drive the threat away. Hard to say. It is not necessarily dominant behavior.
If the JRT is a bitch, you may want to reconsider this whole thing, if they will both be living as house pets. Spaying does not make bitch-bitch aggression any better.
But if she came in today that can also play into it. I would limit interactions with other dogs until she is more settled and then go slow.
Jenna, RN CGC & Babs, CD RA CGC HIC
Heidi, RA CGC
SG3 Odessa, SchH1, Kkl1, AD
Ninja, RN CGC & Milla, RN CGC
Joy, Star Puppy, RN CGC
Dolly CGC & Bear CGC