Translation:She will not be available in the morning.
bydd -> fydd because it is a negative statement. Again, it is one of these things caused by the ghost of a particle which is not used in colloquial speech and informal writing, but which is still used in formal settings.
This time it is the negative particle ni. It takes the 'mixed' mutation - aspirate mutation of p, t, c, soft mutation of b, d, g, m, ll, rh:
- Ni chanietir ceir - Cars not allowed
Ni ddywedodd y Prif Weinidog wrth y Senedd.... - The First Minister did not tell the Senedd...
(Ni) Ddylet ti ddim gyrru ceir yma - You should not drive cars here.
- (Ni) Phrynaist ti mo'r car 'na - You did not buy that car.
- (Ni) Wnewch chi ddim gyrru'r holl ffordd 'na neithiwr! You did not drive all that way last night!
Some people do not bother with the aspirate mutation in colloquial speech (I think that Dewi Lingo ignores it sometimes) and use the soft mutation instead.