Sometimes, what APPEARS as a "refusal" or a "change" in nap habit, is them hitting milestones or a developmental change. Then the phase passes and it goes back to normal.
Before you move her nap time to just once a day, I would keep to what you are doing, since this seems to be her pattern and a good sleep routine you got going.
Then, after a time, if it doesn't work, then perhaps move her to 1 nap a day and consolidate it so to speak.
My son is 25 months old and still takes 2 naps a day (morning and afternoon). It's not ME that is "making" him nap, but he gets tired and this is his pattern. But yes, I keep it consistent. Same time, same pre-nap routine- everyday.
I did try to "skip" his morning nap one week... to see how he'd do and so I could take him to toddler groups/classes....BUT, it didn't work with him and it just made him super tired and clingy and grumpy. So, I reverted back to his nap "schedule." When and if he starts to outgrow the morning nap, then I will go according to his needs. The 2 naps a day still works for my son... if he only naps once a day, even for a long stretch... he still gets too tired by afternoon and can't last the whole day with only 1 nap.
If you don't need to, I wouldn't "change" her nap routine/timing. Like any baby/child, they sometimes go through hiccups in their sleep length/times. Its normal.
Each baby/child is different. There is no one "rule" as to when to switch a child to just 1 nap. Go according to your child.
Good luck,
Susan