Yes, this is football, and anything can happen. Some key Barcelona players can have injuries, and Barcelona will struggle to win matches in the league. It is not certain that Barcelona will finish in second place in the La Liga table; if Barcelona fails to win most of their remaining matches in the league, Girona might take their position back. After all, Barcelona is just leading by two points.
Two points ahead of Girona for Barcelona is something that is still not safe for Barcelona, especially since at the moment there are still remaining matches that must be won by Barcelona apart from still having to think about the UCL. So Barcelona still has to fight hard to stay in second place in the standings, because if for the remainder of this season Barcelona does not become more consistent in maintaining that position, the possibility for Girona to take back second place in the standings is very wide open.
I made it clear that it's not certain that Barcelona will finish in the second position in the La Liga table if they fail to win their matches. Barcelona needs to win at least seven matches out of the nine that are remaining for them in the league if they want to finish in their current position in the La Liga table.