Little sister has shown interest in wanting to play softball.

[YOCOACH]

At this age since she's just starting, work on the fundamentals as others have said. Throwing mechanics, fielding footwork, proper glove positioning, catching, swing mechanics/hitting etc. The more you and your brother work with her at home, the faster she will develop and it will pay huge dividends in the long run for your sister. Leave the game situations, cutoffs and everything else to the future coaches.

 

[mogsoftball]

Here 8u is still coach pitch. Just teach her how to throw and catch properly and how to properly field a ground ball.

On a side note as a catcher you really need to know how the other positions work. You are the field general and need to be able to anticipate the moves each fielder is going to make based on whats happening on the bases. You need to be calling out plays and situations to your fielders.

 

[dbronstein]

...but don't be surprised when she's better than you sooner than you expect.

My experience is the youngest sibling usually ends up being the best player. They always have to go all out to try to beat the older ones, and they have less fear because they've been going against older/bigger kids all the time. Obviously this isn't an absolute but I've seen it happen an awful lot.