Nortriptyline would be my pick as it has very low serotonergic activity with relatively strong action at the acetylcholine muscarinic receptors which induces constipation, dry mouth, etc. The extra boost from its norepinephrine reuptake inhibition could help with anxiety and depression too.
If Ancient Melody (AM) were to take both the Lexapro(Escitaloprom) at 20mg and the Notriptyline (Pamelor) together (which leads me to ask how much Notriptyline would you recommend, would it be a starting dose of 50mg), would it be better to settle on this SSRI/Tricyclic combination for a few months (such as three to four months), and if things were stable after a few months, then have AM slowly taper off the Lexapro, so she only has the Notriptyline (Pamelor) in her body? For me, that would be preferable, because she would only be working with one psychiatric medication in the long run.
However, if she were to switch from Lexapro 20mg (by tapering off it in two weeks), and then getting on Notriptyline (Pamelor) full time at (say) 100mg, without the Lexapro, this action would probably be riskier, because 1) her body would have already adjusted to the Lexapro, but the sudden loss of loosing the Lexapro in her system could cause more side effects, since the body has to readjust quickly and 2) her body would have to relearn to adapt to a new antidepressant too quickly, like two weeks, by this sudden shift to the new medication, Notriptyline(Pamelor)? For me, this would be less preferable then the first choice, because although both options lead to one psychiatric medication to handle the anxiety, the second option seems riskier and harder on the body, given its short time to adjust.
Of course, AM, this is all conjecture. If anything, your psychiatrist should be determining the final outcome of how she prescribes your medication.