what other fish do you have in the tank? if none of them are carnivorous or aggressive, it may be ok to just let her out in the tank. she'll still give birth. the only thing the net does is

 a) keep her from being harrassed by aggressive fish or males in the tank,

 b) save any fry she doesn't eat (she will probably leave them alone, but might eat a few.),

 c) keep small fry from being attacked by larger fish.

    how can you tell she is pregnant? if you look at her from behind, does she look sort of boxy? the dark spot doesn't always mean they are pregnant. gravid spots start showing up in females 2-3 weeks old, far too young to reproduce, especially if they are in a fry only tank, with no developed males.