1) is it true that personata x fischer hybrids are bad?
In my opinion, creating hybrids is bad. I really dislike that it happens. I understand transmutation however for the average Joe, it´s best for us to stick to breeding within the same species.
2) should i just put a nest box in her cage? because i'm pretty sure she will lay eggs anyway and i want her to be comfortable.
No. It will encourage her to sit longer than she might have had she made a little nest on the cage floor. Lovebirds are stubborn enough, it is already challenging to get them out of the cycle.
I will give mine a little paper to shred if I know an egg is 100% coming, so I let her make a mini nest in the corner of the cage floor. When I clean the cage, I trim the nest down so it doesn´t get enormous, and just leave enough for her eggs (the dummy eggs) to sit on and enough space for her to sit nicely without being awkward on the cage bars.
Some won´t give anything, but I like you also feel guilty and let my 2 girls have a little slither of a nest.
3) i have dummy eggs ready, so i just replace when she done laying and hope she will get tired of them?
As each egg is laid, switch it for a dummy. You have a few days to make the switch in case you don´t have the time or energy on the night the egg is laid, you can leave it til the next day and switch it when you have the time to do it. Some girls won´t give up those eggs without a fight, the best thing to do is coax your hen out with millet or nesting materials to forage, and then switch the egg while she´s out.
edit; I missed half of the question. You can let her brood those eggs for up to but no more than 22 days. Hopefully she will tire of them before the deadline, it will be apparent by the eggs sprawn (not together), and the ¨nest¨ destroyed, or the eggs out of the ¨nest¨. Be sure she has abandoned the eggs before removing the dummys and any nesting material remnants. If time is up and she´s still sitting, you need to give her a push. Rearrange the cage, move toys, add new toys, move water/food bowls, perches etc move the cage if you can, or rotate it, see if she will abandon the nest of her own accord. If not, remove the dummys and any nesting materials, and rearrange the cage as before.
Does you hen eat pellets and veggies?