Now this is a sticky situation

If by "sticky" you mean "There's about to be ***ing murder". Assuming that's Robin, of course. Which by Tharja's expression, it is.

When your look-alike stand-in steals the object of your fascination.

CGrascal said:

When your look-alike stand-in steals the object of your fascination.

Not a lookalike. Tharja is canonically implied to be a reincarnation of Rhajat, according to dialogue in Fire Emblem Fates, and it's also implied Robin is a reincarnation of Corrin.

Garrus said:

If by "sticky" you mean "There's about to be ***ing murder". Assuming that's Robin, of course. Which by Tharja's expression, it is.

I mean there's dialogue from Rhajat in Fates that implies she and Corrin will reincarnate and she'll continue stalking him, which is heavily speculated to refer to Tharja and Robin in Awakening.