The Leaky Cauldron

Honestly, he should have married her

I'm not sure about that. While she's a wonderful and kind person, she is also super weird in a way that I don't think Harry was ever comfortable with.

she was in a unique position to understand and relate to Harry’s problems and needs

If anything, I would argue that Ginny, having also been possessed by Voldemort at one point, was in an even more unique position. They share a nice moment in OotP which was (like most of Ginny's best scenes) not included in the film:

‘Yeah?’ growled Harry, his hands deep in his pockets as he watched the snow now falling thickly outside. ‘All been talking about me, have you? Well, I’m getting used to it.’
‘We wanted to talk to you, Harry,’ said Ginny, ‘but as you’ve been hiding ever since we got back –’
‘I didn’t want anyone to talk to me,’ said Harry, who was feeling more and more nettled.
‘Well, that was a bit stupid of you,’ said Ginny angrily, ‘seeing as you don’t know anyone but me who’s been possessed by You-Know-Who, and I can tell you how it feels.’
Harry remained quite still as the impact of these words hit him. Then he turned on the spot to face her.
‘I forgot,’ he said.
‘Lucky you,’ said Ginny coolly.
‘I’m sorry,’ Harry said, and he meant it. ‘So … so, do you think I’m being possessed, then?’
‘Well, can you remember everything you’ve been doing?’ Ginny asked. ‘Are there big blank periods where you don’t know what you’ve been up to?’
Harry racked his brains.
‘No,’ he said.
‘Then You-Know-Who hasn’t ever possessed you,’ said Ginny simply. ‘When he did it to me, I couldn’t remember what I’d been doing for hours at a time. I’d find myself somewhere and not know how I got there.’
Harry hardly dared believe her, yet his heart was lightening almost in spite of himself.

- OotP, 23