You can but you should plot reset to ensure she goes there. Just because it's clear doesn't mean she'll automatically go there. If her plot is already placed it's too late (unsure by what you mean moving in tomorrow if you mean her plot or her house and her physically)
- - - Post Merge - - -
I'd recommend moving your hybrids to a fence/inventory or locker or someplace by a pwp so if something goes wrong they're safe
If you want merengue to have her house in a specific spot you are going to have to plot reset.
Otherwise she can place her house anywhere there isn't a PWP or rock.
She can move on top of flowers, trees and bushes.
Oh okay that clears things up, wasn't sure if her plot had appeared because some people consider that "moving in". You can clear off a space for her but you have to plot reset to ensure she goes in that space exactly
Its when you create a new save file just before 6am on a day a new villager will place their plot down, to decided where you want their plot to be. Because the save file is new and hasn't been saved, you can just exit out of ACNL if you don't like where the plot is
For example
1.Mayor tt's to 5:58 on new day
2.Wait 2 minutes and player starts up new save file
3.Player goes through everything and before heading to townhall/nooks goes to look for plot.
4.Plot is on top of hybrids/orchard or some place the player does not want the plot to be
5.Player exits ACNL by clicking home button and closing ACNL
Excluding first two steps, the cycle is repeated till the plot is in a good spot
Flowers and trees have nothing to do with it, because when a villager moves in they can move in on top of flowers and trees (though it's a good idea to remove flowers you want to keep). The only things that block a villager from moving on certain spots are things like rocks, ponds, and other buildings, the same things that Tom Nook will take into account when you're plotting your own house.
If you're concerned about it, just plot reset. You basically save the game in one day as your mayor and then start the game on the next day as a new character. Don't go to the town hall or otherwise save as that character, just exit the train station and look for the plot. If it's somewhere you don't want it to be, quit the game without saving. If it's somewhere you want it to be, go through the steps of saving your game (you can then delete that character, don't worry). The process is based on the fact that if you load the game as an existing character, your town will be locked into the state it is when you load, so the plot won't move around. If you start as a new character, the plot won't be locked into a specific spot so you can reset to put it in a different location.
People usually tell you about setting the clock to 5:58 as your mayor (because a new day in the game starts at 6 AM rather than midnight), quitting immediately, and then waiting until it would be after 6 AM (in the game) to start as a new character. That's one way to do it. If you don't mind using the 3DS clock instead of Isabelle, you can set it to the next day and start as a new character right away. You can also wait for the next day in real time (so if you invited in Merengue and then went to bed or something and will only be playing the day after, you can plot reset right away if it's after 6 AM).