I'll try to at least put things in perspective as best I can as to why people suggested Lullabelle to be the strongest of the Low 2-C tier.
Lullabelle is consistently referred to as the second most powerful being in existence, second only to her Father/God himself (and the Divine Calamity which is essentially equal to God).
This does NOT only refer to one specific tier. This basically means that no matter what version the characters are in (such as restricted selves, avatars, and so forth), Lullabelle should be above them, this includes their hax (and boy do we need to have a talk about that...) Even restricted to her Low 2-C key, not only is Lullabelle is still tremendously above all others in the verse in attack potency (see powerscaling chain I posted on the Wiki's Strongest thread), but she also uses her limitless millennia of combat experience to overcome their hax/ This includes hax of all kinds (in-verse, of course) of which there is plenty in terms of uniqueness and variety, such as Medusa's petrification + mind hax.
About Lullabelle's speed
I wouldn't suggest she gets blitzed without thinking of the unquantifiable nature of her speed. Lullabelle bypasses causality and distance with her speed. On VSB this was debated to be either infinite or immeasurable, but we do not exactly know how such a speed translates to our system.
Lullabelle created the multiverse, which is a 4+7 (11D) multiverse. In other words, 4 spatial dimensions and 7 temporal dimensions. Lullabelle moves in seven temporal dimensions. I presume Taiyomu only bypasses one (not sure, just going by what 99.9% of the FC/OC and VSB communities understand immeasurable speed to be without getting into specifics.) There's no way she can be touched. However, that's only speed unequalized business. Of course I myself only recently figured out how this would affect all of her tiers (then again I remember DarkLK saying lower-dimensional beings couldn't have "true" immeasurable speed) which is why I left it as infinite.
So...who wins?
From my assessment, Taiyomu only has the hax to win this. From what I can see (please correct me if I'm wrong), her AP doesn't stack up to even be capable of making Lullabelle flinch. How? Again, remember that powerscaling chain I posted? That doesn't just refer to High 1-C, but High 3-A, and Low 2-C as well.
That's just my attempt at putting things in some form of relative perspective. I'm very tired so I hope I worded everything correctly and didn't miss anything important regarding Taiyomu.