I’m not a teenage girl, but this isn’t expensive, works with a phone, etc, there are others at their site of course. Best thing I can think of is search for STEM robots for teenagers, that’ll give a good list of things less expensive than Lego’s, which are probably also on that list…
Also, most of the stuff probably uses Scratch or something like that to code, which is a great place to start imo
Cozmo is another one.
Not sure where in the world you are, amazon of course has them, but places like Best Buy usually carry both those here.