In Welsh, the preposition must have a suffix (an ending) to match the pronoun that follows it, e.g. Dywedais wrth Elen na fyddet yn mynd hebddi.

There is no suffix if the preposition is followed by a noun, e.g. chwilio am y dillad, darllen am y bardd.

Nofel is feminine so the third person feminine form for am should be used - amdani.

The full conjugation of the prepositions can be found by clicking here.