Why does she show up and disappear?

My ex and I broke up back in October. Since then, I started to move on. I created a new Facebook, after deleting it during a break we had in the early part of 2018. New email too.
Since then, she's shown up as a suggestion, and I removed the suggestion. And although it hasn't come back, she's started to pop up if I type the first letter of her name
Within a month, she came back, and moved back up the list. And I deleted my activity again, and eventually she fell off the list. But within two days she came back.
Then after a week she disappears or falls off the list.
To my knowledge the only reason this occurs is if the two interact a lot. We have no mutual friends, and I don't post my work stuff. So my friends theorize she is looking up my profile.
Do you think that's the case?
Why does she show up and disappear?
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