Well hey :) I'm Riley (girl) and I'm new to Ultimate Guitar...
This is completely done by ear, so if there are a few mistakes, just bear with me c:
I THINK the strumming pattern is:
D D U U D
Enjoy!

Capo 5th Fret

Verse 1:
            G
You make me happy, whether you know it or not
             Cadd9
We should be happy, that's what I said from the start
        Em7             Cadd9      Em7
I am so happy, knowing you are the one
       G            Cadd9      A
That I want for the rest of my days
                   G
For the rest of my days
                  
You're all of my days.

Verse 2:
       G
You're lookin' so cool, you're lookin' so fly
                           Cadd9
I can't deny that when I'm staring

You down, right dead in the eye
                      Em7
I wanna try to be the person you want

The person you need

It's hard to conceive
         Cadd9               Em7
That somebody like you could be with

Someone like me

Chorus:
    G     Cadd9        Em7     G
I'm happy knowing that you are mi-i-ine
    G        Cadd9          Em7   D
The grass is greener on the other si-ide
    G      Cadd9            
The more I think, the more I wish
              Em7                            G
That we could lay here for hours, and just-a reminisce
    
Ooo ooo

Verse 3:
       G
You're lookin' so fresh

It's catching my eye
                        Cadd9                       
Why, oh why, did I not see this before,

The girl I adore was right in front of me?
             G
And now I'll take a step back and look in your eye
               Cadd9           Em7
And ask why it took so long to see
               A
We're meant to be

(it goes like that the whole song except for the bridge)

Chorus  
I'm happy knowing that you are mi-i-ine

The grass is greener on the other si-ide

The more I think, the more I wish

That we could lay here for hours and just-a reminisce


       F
On the good, the bad, the ugly
    C
The smiles, the laughs, the funny,
   Em                                  G
Or all the things we put each other through
         G        G              G
It's for you, for you, for you.


         
You make me happy, whether you know it or not
             
We should be happy, that's what I said from the start
                        
I am so happy, knowing you are the one
          
That I want for the rest of my days
                 
For the rest of my days


    
I'm happy knowing that you are mi-i-ine
    
The grass is greener on the other si-ide
    
The more I think, the more I wish
              
That we could lay here for hours, and just-a reminisce
    
Ooo ooo

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That was pretty much it!
I hope you liked this tab :D
Rate, please ;)
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Byeee =^-^=