Bal,
You can bring about changes for other people, but only if your intentions are stronger than theirs.
If you read the replies from xkodakmoment, it is obvious that the visualisations, affirmations, etc put out by xkodakmoment were very strong. You will notice they were also quite general, just asking for the person concerned to be happy, or to be in happier circumstances.
The person concerned was probably open to other possibilities, but was just worried or unhappy about their current circumstances. If the other person is open then you have a chance to influence matters on their behalf.
Again, your intentions must be general (e.g. you ask for them to be in happier circumstances). You cannot make them do something that is against their nature, like fall in love with your best friend because you think they would be a good match.
It goes without saying that you should only ever do this when your intentions for the other person are positive.
Peace and love,
Edge.