If a teenager that I created, falls in love with a computer character, and then my teenager grows up, is there a way to make the computer character grow up?

If you make the parent friends with the sim you want to age, and then get them to move in - you can age them when you control them

or

You can get the Sims 2 Freetime

or

You can use the cheat "boolproptestingcheatsenabled true" (without the "") then click on the sim in your house and right click on SPAWN and the TOMBSTONE OF L&D
once this is spawned you can rightclick on this and the other sims to gte interesting effects!

If you click on the sim you want to age click on MAKE SELECTABLE and then click on the tombstone and click SET TO BIRTHDAY after this you click on the sim and click on GROW UP then you have to click on MAKE UNSELECTABLE

I sugest you save a "tester" family and play with the tombstone. You can do alot of great things with it

Using the agesimscheat function yes you can but you have to have the character at the sim's house.

Totally no answer, but couldn't resist my answer. Sounds like the movie/book Portrait of Jenny with Joseph Cotton and Jennifer Jones. Interesting concept and great love story.

In Sims 2 you can have the character come to the house, then get the cheat window up and type in "agesimscheat on". Then click on the computer character, click set age, and then adult. You might have to do an interaction to get the relationship back to love status.

Are they already an adult. If they are move them in. Is this the sims 1 or 2