It is an unnecessary risk here. This is an elective procedure. There is no infection, no unstable fracture, no deformity that won't fit in shoes, etc.
I will do an infected ingrown or ulcerating deformity or trauma stuff for CRPS patients (even with that extremity involved), "uncontrolled" diabetics, alcoholics, morbidly obese, fibromyalgia, etc since those are a major debility or threat which will progress quickly. Joint pain is not those situations. You have to consider the reason that the Morton ext, injects, topicals, better shoes, etc do not relieve her 1st MPJ pain is the CRPS... so how will any surgery fix that component?
It's always a case-by-case basis, so it's ultimately up to you. Some CRPS (and non) patients are anxious lunatics, and some are pretty mellow normal folks with just local involvement. Do at least a few visits and figure out which type of CRPS and which type of personality you are dealing with. Personally, I'd do the conservative care with good pt counseling in the process ("surgery could definitely do more harm than good, and I don't want that for you"). We often forget our role as health counselor/advisor and assume surgical skill can compensate for patients with questionable mental health, physical health, compliance ability, etc (it seldom can). If she is set on surgery, you can send her to a competitor for another opinion (I usually don't do that to someone in my group or someone I like). If you decide to do an elective case for any CRPS pt (I almost certainly would not), then make sure to get neuro/pain consult from her specialist regarding risk.
As someone who has been sued over "causing CRPS," it is never a good thing (case was dismissed nuisance since the pt was on video waking in flip flops when she was supposedly crippled, but still not fun). Any post-op nerve pain will be blown up by the plaintiff attorneys as being new dx CRPS or exacerbation of it. It is just generally stuff you don't want to get involved with if you can avoid it. There is no reason to be a hero and many other patients to operate on. That is definitely one thing I am better at now than I was 10 or even 5yrs ago... detecting the crazies and the anxious ("CRPS-prone") and the unrealistic expectations in pre-op visits. I will often say "you can probably find another foot doc who will do the surgery for you, but I am not going to be the one as I do not believe it's in your best interest" (used if pt wants ultra-fast recovery, can't be NWB, almost any nerve surgery, MPJ implant, ankle implant, salvage when amp is clearly best move, various anxious or unrealistic expectations or unhealthy pt, etc). Again, sometimes with infection or trauma, you have no choice, but in elective recon, you always do. Don't roll the dice when there is no reason to.