Encourage her to build and create things. If she chooses the computer as her tool, all the better, but provide her with as many avenues of creation as possible (paper, sound, words, images, code, wood, ideas, etc) and she will find the one that's right for her.
She is a teenager, I believe you are not her guide anymore, but you can (and should) be an amazing facilitator and her #1 fan.
Does she like math puzzles? I came across this recently, about Mary Somerville. She's not exactly Ada Lovelace, but close.
At the age of fifteen she came across a mathematical puzzle in a ladies magazine (mathematical recreation columns were quite common in ladies magazines in the 18th and 19th-centuries!)
The only one she didn't enjoy was cooking so I didn't send her back. But she does ask me for more girly stuff though I don't know what that looks like :(
I know one of top female coders in Google who worked on Maps. She said her dad taught her a few things in java when she was young. Her dad would give her some sort of reward of every little school problem she could solve with java. Before she even grew boobs, she made a word problem solver based on the STUDENT paper http://dspace.mit.edu/bitstream/handle/1721.1/5922/AIM-066.p...
Any suggestions from HN on how best to guide her interests?
Extra project? incentive?
For now, her interests are typical teenage - school clubs, facebook, youtube, tumblr, etc.