<human>: Throwaway since I think my daughter lurks on other subs

A bit of back story:

My ex and I had my daughter young (I was 21, she was 20). We had a horrible breakup when my daughter was nearly one. Long story short, soul sucking custody battle ensued for nearly ten years. 

Obviously this had a lot of repercussions, along with what I consider to be an unhealthy relationship with her mother (I'm sure I'm at fault too). She was heavily into drugs by the time she was 13. Things were insane for two years (multiple runaways, crimes, violence, etc.) Finally her mother and I sent her to rehab at 15 and she cleaned up. 

Things seemed to get better; she got her own place, a job, went back to school. She moved in with her boyfriend (21) and stayed with him until she was 17 (I wasn't happy about this, but let it be). They broke up and I thought she might finally get to experience a "regular" teenage life.  

At 18 she moved in with myself and my wife, and everything's been... fine. But that's the problem. It's just fine. I feel like she's wasting what are supposed to be the best years of her life. 

She has a few friends, but they're all significantly older then her. She doesn't go out since she doesn't drink. I know she goes to the gym and runs, but she does that alone. She's friendly but reserved. She's in college and gets good grades, I think she likes her courses, but she's not passionate about them.  

Recently she told me she's been seeing this guy... who's 28. She told me he's nice and that it's "casual". As much as the age gap worries me, at this point I could handle it if she was actually in love with the guy.

Everything she does reminds me of a 40 yr old who's resolved to live an average life. Part of me wonders if I should just let her be, but I think it's wrong to let her waste her life.

Can you condense the text into a few key points?
<bot>: I think my ex-drug addicted teenage daughter is wasting her teenage years and I don't know how to help.