You say that you have a fish tank in your room?
Well! If you wanted to cycle your sister's new tank in a few days just simply put the filter media from your tank into her new filter, plus a little stocking full of your gravel. The tank should be cycled in a week.
To aid in this process though, because you need to feed the bacteria from your old filter, put the betta and a few cories into the new tank. Bettas can breathe surface air and cories are really hardy. They will produce waste to help the bacteria multiply to cycle the new tank.
I cycled my 33 gallon this way- i added the sponge from my 20 gal filter into the new filter and added my betta and three pepper cories. The tank cycled in 5 days and was ready to go- and everyone was happy and did really well.
This is the easiest way- and because you aren't realy so much 'starting from scratch' the fish won't be really hurt by the cycling process.

Well! If you wanted to cycle your sister's new tank in a few days just simply put the filter media from your tank into her new filter, plus a little stocking full of your gravel. The tank should be cycled in a week.
To aid in this process though, because you need to feed the bacteria from your old filter, put the betta and a few cories into the new tank. Bettas can breathe surface air and cories are really hardy. They will produce waste to help the bacteria multiply to cycle the new tank.
I cycled my 33 gallon this way- i added the sponge from my 20 gal filter into the new filter and added my betta and three pepper cories. The tank cycled in 5 days and was ready to go- and everyone was happy and did really well.
This is the easiest way- and because you aren't realy so much 'starting from scratch' the fish won't be really hurt by the cycling process.