Plot Contrivances - the bane of my writing life!

In my revision letter, I was pulled up a lot on 'plot contrivances'.

One eg. 'It did feel very coincidental that P and C ran into Tim (that's her nasty ex btw) and his wife together.'

In the above scene, running into her ex-fiance with the hero triggers an important conversation about P's backstory and conflicts. The editor however wanted me to think of another way to make this happen. She suggested maybe they run into a doctor who delievered some bad news to P instead.

Now I can see how this is slightly less contrived - cos both P and C are working for a children's charity in a hospital and therefore could more likely run into a doc. But it STILL feels a little contrived to me.

I find it really hard to decipher what's contrived and what's an okay coincidence!?

Take the BM (which I've written in the original incarnation but am not up to in the revised version yet). P cooks a lovely, romantic dinner for C and just when she's expecting him to turn up, another man who really, really likes her, turns up instead and is in the throws of proposing to P when C arrives. I've hopefully foreshadowed this enough through the story so that readers won't think 'What the?' when he does. The reason I wanted the other man to show up is that I wanted C (the hero) to realise that in just having a 'fling' with P, he's holding her back from what she really wants. Then he sees the hugely romantic dinner laid out and freaks.

This triggers a heated discussion where he makes her confess that she does want marriage, babies, the whole shebang and he leaves.

So my question is... is the other man a plot contrivance or because I've foreshadowed it throughout and am using him to make C sit up and think, is it okay? Would love to hear your thoughts.

I could do this scene without the other man. Have C come upon the romantic dinner and simply freak out, but personally I think it's much stronger if he sees that there's someone who loves P enough to want to give her marriage and babies and so he realises he should take himself out of the equation. But I could be too close to this, so I'd love your thoughts and opinions.

I think I've realised I actually quite like it when external forces (not earthquakes and fires etc, but things that are more likely to happen) give the hero or heroine a shake-up! Perhaps that's my downfall - I like a bit of action :)