This is canon dialog.

Reimu says this word-for-word if she wins in VS mode when paired together with Marisa.

There is one difference, but it doesn't change anything: the in-game text says "Marisa" but is read as "you", while here it just says "you".

they are talking about battle strategies. it must be love!

Well, more like Reimu had hoped and expected to partner up with Marisa, and she would have liked to because she thinks she and Marisa would be unstoppable. It's a cute little sentiment. Not outright yuri, no, but it shows that she respects and admires Marisa to the point that if she had a choice, she'd pick her first.

Vid-szhite said:

Well, more like Reimu had hoped and expected to partner up with Marisa, and she would have liked to because she thinks she and Marisa would be unstoppable. It's a cute little sentiment. Not outright yuri, no, but it shows that she respects and admires Marisa to the point that if she had a choice, she'd pick her first.

This is completely consistent with the manga. The two have one of the deepest platonic-almost-romantic friendships in all of fiction. In fact I could've sworn I read somewhere that game mechanics aside, the two are generally said to work side by side during most incidents where they're not in direct competition.