i'm right handed but when i started playing i wanted to play lefty. but my brother wouldn't let me touch his guitar if i played lefty, and my parents backed him up and kept telling me i had to switch if i wanted to be any good. yeah, like they knew 
on one hand, i'm glad they did because even though lefty basses are available, they're not nearly as common and they're almost always more expensive. plus, if you're a lefty, you can't just pick up someone else's bass and sit in with it. but i can't help thinking that maybe i could have been a better player if they let me play lefty because it was natural to me. being lefty never slowed hendrix down, or wayman tisdale, or elliot easton, or paul mccartney, or any number of lefties who became great players. too late now to worry about it, though.
if she were my daughter, i might tell her that manufacturers cater mostly to rightys, but i'd let her make her own decision. being a lefty is not a bad thing at all. righty teachers can easily teach leftys with a mirror, and if she feels more comfortable that way, she'll probably end up being the better for it. she'll certainly feel like playing more often than if she's forced to conform. while it's true that i've never seen a classical violinist or cellist who plays lefty, she IS wanting to play bass and not violin. i say let her try it.
on one hand, i'm glad they did because even though lefty basses are available, they're not nearly as common and they're almost always more expensive. plus, if you're a lefty, you can't just pick up someone else's bass and sit in with it. but i can't help thinking that maybe i could have been a better player if they let me play lefty because it was natural to me. being lefty never slowed hendrix down, or wayman tisdale, or elliot easton, or paul mccartney, or any number of lefties who became great players. too late now to worry about it, though.
if she were my daughter, i might tell her that manufacturers cater mostly to rightys, but i'd let her make her own decision. being a lefty is not a bad thing at all. righty teachers can easily teach leftys with a mirror, and if she feels more comfortable that way, she'll probably end up being the better for it. she'll certainly feel like playing more often than if she's forced to conform. while it's true that i've never seen a classical violinist or cellist who plays lefty, she IS wanting to play bass and not violin. i say let her try it.