Woof

To be honest, I would also do the same. If she didn't mean it, and you tried to advance, that would be embarrassing and ruin a good thing. Things like that should be said way more explicit by both parties

If Heather is smooth enough (which you could argue either way based on the other party not realizing it's a date), this is her opportunity to pivot hard into it being a date. Say something mildly sappy and emphasize it really being a date, go for the kiss.

I mean, I think the fact that this 10+ year old meme (posted on Relationship Memes of a places) is fake, is common knowledge. At least say a joke as part of the takedown! Make your comment interesting! You've been given the gift of free will, and the ability to say anything, use it!

Not assuming they are straight