Not knowing the speed your wife throws at, or how her El Nino ball is laid out, makes this a difficult reponse.
Also, it's been quite a while since I've seen an El Nino thrown, so that makes it doubly hard to compare.
But I will say this, most pearls of any kind are skid-snappish on clean, dry backends.
The Mars will offer your wife good control, with a very smooth transition on the backend, followed by good energy at the pindeck. This is a very good ball for the conditions you describe.
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Some days you're the bug some days you're the windshield.