Just google for this:

Dallas chicken ordinance

and it should come up with the answer.

I am not a lawyer, but it looks like you have grounds for a complaint: the chickens are not restrained -- i.e. they are able to leave the neighbor's yard (you may want to take photos as evidence of this); they are kept in unsanitary conditions (depends how recently the neighbor has cleaned); the smell may be a violation as well (depends how recently the neighbor has cleaned). I don't know if you have any hope of convincing the inspector that the coop should not be on the property line.

Since the neighbor is clueless, you might want to show her the relevant parts of the Dallas City Code:

SEC. 7-2.5. IMPOUNDMENT OF ANIMALS.
(a) The director or the chief of police is authorized to impound:
(1) any animal in the city that is not restrained by tether or leash, fenced yard, or enclosed structure....

SEC. 7-3.1. PROPER RESTRAINT.
(a) An owner of an animal commits an offense if he fails to restrain the animal at all times in a fenced yard, in an enclosed pen or structure, or by a tether or leash....

SEC. 7-3.2. SANITARY CONDITIONS; MAINTENANCE OF PREMISES.
(a) An owner of an animal commits an offense if he fails to:
(1) keep any cage, pen, enclosure, or other area in which the animal is kept in a sanitary condition; or
(2) remove all animal excreta from the cage, pen, enclosure, or other area in which the animal is kept as often as necessary to maintain a healthy environment.
(b) A person commits an offense if he permits any yard, ground, premises, or structure belonging to, controlled by, or occupied by him to become nauseating, foul, offensive, or injurious to the public health or unpleasant and disagreeable to adjacent residents or persons due to the accumulation of animal excreta. (Ord. 26024)

http://www.amlegal.com/nxt/gateway.dll/Texas/dallas/volumei/chapter7animals?f=templates$fn=default.htm$3.0$vid=amlegal:dallas_tx$anc=JD_7-7.4