I recently tried the love potion/honey "cheat" on my masktchi.
To obtain the love potion, go to the shop screen. From there, press the 'a' button a few times until the shopkeeper makes a surprised expression. (Press the button about three times). From here, type in BCBC CABA.
When you give it to your adult tama, I recommend having another tama that you would like to become partners with around. The first thing you will see are hearts on the tama that you fed the potion to. Then connect with another adult tama. I chose 'visit' for mine. There will be alot of hearts and they will smooch! It is totally adorable.
After I used this, both of the tamas were partners, ie. at four hearts.