I actually think Sela's grudge is more fundamentally against the whole of Starfleet, but with some emphasis on her mother who she now looks at as traitorous. Hell, she's clearly aware of who Picard is, through her mom's recounts & general Romulan intelligence. I bet Sela even suspects some kind of conspiracy from Picard & Tasha, to alter their past & perhaps subvert the Romulan Empire. If you look at it from her perspective, it can seem pretty underhanded, that they'd send someone from the future to alter events relating to a Romulan engagement
I guess this was TNG's own Temporal Cold War.
You know, I hadn't thought about it like that, but yeah. I'm surprised that with the information Sela knows, the Romulans haven't gone off on their own temporal warfare track. Tasha coming into the past can clearly be considered an attempt to gain temporal advantage