There is no "formula" for this, and each child is different. But, at 13 months old, they still need a nap. It even helps them developmentally. Even Preschool and Kindergarten aged children have a 'nap' or quiet time.
Just be cautious, about forgoing naps completely. This is sometimes done, but is jumping the gun. Kids will sometimes have nap quirks (due to growth changes/developmental changes etc. as Deanna Leigh mentioned), but it will go back to their regular nap times/routines.
The thing is, you need to cue into her, each day, and put her to nap accordingly.
If she needs to need a morning nap, then do so.
If she seems to need an afternoon nap, then do so. She MAY not actually nap, in the afternoon..but if she 'plays' in the crib... this is likened to her "quiet time" and as long as she is fine and content in her crib playing (not crying or screaming), then you can leave her be in the crib, with no interruption on your part. My son does that too, even for an hour sometimes, just playing/talking in his crib himself completely happy and content. He has his favorite toys in his crib, and he is independent and knows himself.
For me, my 2.5 year old son, STILL naps twice a day (about 90% of the time).... around 10-10:30 (for 2 hours) and in the afternoon after my daughter comes home from school around 3:00-3:30 (for 2 hours). BUT, if he does not seem to need a morning nap, which happens sometimes, then he too just "plays' in his crib, contentedly, and does not complain. When he does start to call for me, then I take him out. He knows that.
My son, since I know him so well, I know when he 'will' nap or not. And when he needs to nap, or will, or will not take his 2 naps a day. Then, I just put him down for 1 nap a day. BUT, everyday, he DOES nap. Always. He cannot last all day without one. Then he goes to bed at night around 8-8:30 and wakes around 7:00am. He is very regular.
I have tired 'consolidating" his naps, more toward noon time... but he gets too tired by then if I skip an earlier morning nap time. BUT....if he naps around noon time, then by the late afternoon, he gets tired again... but because he had a nap later in mid-afternoon, he often cannot nap or cannot nap well at this point. So, I have learned his rhythm, and what is a good time or not, for him to nap.
This routine I have for my son, works for him. My daughter, who is 6 years old, will still sometimes nap, in the afternoon when my son is napping. They are BOTH napping now in fact.
It's finding your child's rhythm, and cue into them.
BUT, the main thing is to have a consistent constant routine....for nap and bedtime. Its easier that way, than to forgo napping altogether, and then having to back-track and then try to get the child to nap again... once you've gotten them out of the 'habit.'
For me, I DO make sure I am home, at my son's nap times, and after-school when my daughter is done with school. I like to keep him/them regular, and I know my son gets tired and naps. He will even tell me when he is tired or needs a nap sometimes. And he will go about getting into his routine. There is no protesting on his part. He just does it. So for me and my kids, this works.
All the best, just my own experience with both my kids,
Susan