How do I help DS through this?

[DreadPirate]

Hi all, would appreciate some advice on this.
DS(21) met a someone and they had a short, intense, few weeks together. She then ended it. DS has some mental health challenges and he really hit rock bottom after that. He also has OCD and it really created some problems with this. I’m not in any way blaming this on the young woman.

Anyway. He found out the other day that she’d apparently “used him to make the ex-boyfriend jealous”. Around the same time she messaged DS asking to be friends again, saying she needs “more good people in her life”

I want to beg him to stay away and just re-start his treatment and get better.

How do I navigate this with him?

My 20yo is an opinionated young thing who has had his fair share of heartbreak already but wouldn't respond well to me directly telling him what to do.

I ask lots of questions which try to steer him towards making his own (good) decision.
'how would you feel if...?'
'why do you think she...?'
'what will you do if...?'
'what do you need to do to be happy?'

If I have a similar tale of my own where everything went tits up, I might share that too.

Thanks @Sugarnspicenallthingsnaice, that all sounds very sensible.
DS also opinionated and wouldn’t be happy being told what to do!