>>25199490>I will now proceed to drastically over-analyze silly drawings about japanese cartoon monstersThe way I see it, it's largely explained by the
>>25184052 pic. He found her as a shy little Ralts, probably one of the first mons he actually caught considering how early in the game they show up. I could even see her being his first capture, and at the very least she's probably the second longest-standing member of his team after Sceptile.
Then you've got
>>25185533, which I didn't even realize was the same artist at first given the tone shift. If you want to argue that this takes place in whatever 'canon' this series has (and isn't just a random cool scene the artist felt like drawing), then she likely saved his life at some point, at great risk to her own. That'll go a long way towards smoothing out any discomforts or awkwardness.
Basically, despite being kind of weirded out by how aggressively she's pursuing him, there's too much love on both sides of the relationship for him to send her away, and she'd never dream of doing anything to hurt him.
But goddamn does he wish she'd chill the fuck out.