Maybe a steering dampener that is adjust able.
Reading what you discribe, yes, keeping in mind that if too soft wobble will be back. It may become hasardous with a physical strengh issue.
May be your wife hasn't completly recover, it takes a lot of time to rebuilt muscles....
Check with a spring balance how much is needed.
Tire pressure. 40 all around
Tire wear and shape/type. brand new tires all around
A bit like what oil you use. Lucas Synthetic SAE 20w-50
Steering bearing adjustment/wear etc. 4,000 miles on the bearings
Set up adjustments etc, same before
The list can be long.
Reading what you discribe, yes, keeping in mind that if too soft wobble will be back. It may become hasardous with a physical strengh issue.
May be your wife hasn't completly recover, it takes a lot of time to rebuilt muscles....
Check with a spring balance how much is needed.
My wife was not the one test driving the bike, I was. I won't let her get on it if it is not safe. Not sure what a spring balance is. Thank you all for the advice.
Beetwen the handlebar and your hand, compare how much is needed for you in order to start moving and compare with how much she can apply.
May be, if she doesn't use it, start training with inertia applying brakes, once you can manage it, its a gamechanger, the only disadvantage is for the passenger, its harsh and tiring.
Dennis @dennis-peabody, you know, that I know the answer you seek.
Send me 3 newly baked loaves of Sourdough bread, and I shall reveal the answer. 
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Okay, okay.....answer for free, only because you are a fellow Washingtonian, and I like your wife's Sourdough bread too much to use it as a bargaining tool.
Use a lighter weight (read that as lighter resistance) steering dampener. It does not NEED to be an adjustable steering dampener, although that might help you fine tune exactly the sweet spot necessarily to eliminate 93.14 % of the wobble.
Your tire pressures are a little on the high side, but that is your choice....actually your pressures are better than being a little on the low side, so stay high if that is what you choose.
After the first 500 miles to 1,000 miles, retorque those steering head bearings, as that allows them to settle in, then be set at the right torque. Technically NO need for an actual torque wrench, as experienced mechanics do it by feel.
Question: does this wobble occur with both hands still on the handlebars, or only when one hand on, or no hands on the bars ?
Does this wobble occur only when deaccelerating, as in letting off the throttle, or also whilst gently accelerating at lower speeds.
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Hmmm...I can foresee at least one loaf of Sourdough in my future.
Two Million Mile Rider
Exploring the World in Comfort
@miles-ladue The wobble occurs with both hands at the lower speed as you accelerate and when at any speed when you hit a bump accelerating or de-accelerating. As for the sour dough bread you know where it is located.
Dennis, I would have to ask....in YOUR opinion, just how bad or severe is this lower speed wobble ?
Example: I have a very low speed wobble in the front end of my 2019 Goldwing w/DCT and Hannigan Dream sidecar, but it is highly unlikely that I will ever be able to install a steering dampener on this front end, because of design factors. A few of us have looked at this, and we all scratch our heads.
My answer to my front end wobble is, I just live with it, as I can very easily control it. In your case, it is your wife that will be operating that Sporty.
With the Sportster, it is easy peasy to install a steering dampener, ergo...given all the things you have tried thus far, I suggest either a lighter resistance steering dampener, or an adjustable one.
And yes, I know where all that Sourdough bread is made....at your house, in the kitchen, and stored in the best smelling bedroom.
Two Million Mile Rider
Exploring the World in Comfort
@miles-ladue The low speed wobble is not the worry it is just the wobble at higher speeds when hitting bumps. The bike had a steering dampener on it before, but still made the front end stiff to turn, thus the thinking of one that is adjustable.
it is just the wobble at higher speeds when hitting bumps.
sidecar shock hidraulic.
The bike had a steering dampener on it before, but still made the front end stiff to turn, thus the thinking of one that is adjustable.
and may be in a different location/position.
This is the type of damper I have on my rig, adjustable and normally a bolt on item. I stole the pic from the Dennis Kirk site, so check there. I run a Sportster fork on a rigid bike, with an old style ribbed tire. I don't have any wobble, but that tire grabs every road imperfection and I get a wiggle. The damper helps control that well.
I don't know if you are doing the work, so I won't go into the steering head adjustment (fall away). It is simple, but must be done as the factory manual dictates. The measurements and torque sequence are important, to get it right.
What model Sportster? Some have small narrow handle bars, (XLX style) some are wider, (FXDX style) and some help smaller riders, (super low style). You may be able to give your Wife more mechanical advantage with a bar/riser change. I've done that many times, including for my Wife's Sportsters and Dyna, and also customer bikes.
