and I'm worried that an older guy or gal will teach her behavior more in keeping with hound-dom, as it were.
By the time a dog reaches 18-2yr old the personality is pretty much set in stone. A bidable (willing to please) dog will remain so. But it is important to seperate behavior from personality. It is posible for a dog learning simply by observing another dog. A dogs ability to do this is extemely variable, So could a new acquision teach lollipop to counter surf, yes especial if the behavior has an intrinsinct reward.
I'm equally sure she would be jealous at first as an only hound
I think it is extremely dangerious to asign emotional causes for dog behavior especial one so charged as jeloousy. For example resource guardiang can be explained without any need to invoke "jelousy" Also what is often mistaken for jelousy in multidog household is nothing more than rude and obnoxious behavior that is unwittingly rewarded by the humans in the household. When petting one dog and the other comes up to be petted butting in. Is the dog being jelous of the attention the other recieves or is it simply a learned behavior that the surest wat to get attention or a pat is to butt in while another is getting one? In a single dog household it is very easy to overlook these type of pushy, rude and obnoxious behaviors, In a multi dog household not so much. I would recoommend
Feeling Outnumbered - How to Manange and Enjoy a Multi-Dog Household for a fair review
click here
The guiding premise of the booklet is the value of teaching "polite, patient, and respectful" behaviors and making a conscious effort to reinforce these in situations where dogs might otherwise be pushy and demanding. The authors point out that, left unguided, many dogs will get pushier as they grasp for their own rewards, resulting in a mob of rude, potentially contentious dogs.
Would the benefits of another hound outweigh the possible behavioral side effects on Lolly
What behavioral side effects? You do yourself a diservice if you asign her personality etc as the reson for her good behavior, rather than you ability to train and manage the household. Now whether a second dog is a possitive thing for lollipop only you can acurately assesses.
Toughy was over two and an only dog up until that time. It was quite clear he was rather aloof and would not really benefit from a second dog. Did his personality change No. did his behavior change, no. De he engage in a lot of play or general enjoy the presence of the other dog no. It depends on the dog. In hindsight if the new dog was male he might have been a bit more responsive. As it turns out the only dogs he played with were other males. So the idea that it is best to have opposite sex pairs is not always true it really depends on the dogs involved.
My Wife Nora and I are considering adopting a hound from the NEBR (New England Basset Rescue), ... I'm worried that an older guy or gal will teach her behavior more in keeping with hound-dom, as it were
Keep in mind a rescue need not necesarily be older than lolipop. I am currently fostering an agility prospect for them that is under 1 year old. There are youngster in the system.
She is still young (just over a year) so I'm hoping as show grows she will grow into Ringo 
