'Straight', as Jarvis uses it, tends to have a meaning more like 'square', or otherwise un-groovy. 'it must be great to be straight', in this context, would refer to his envying the security that she feels, now that her life has become more dull and routine after settling down.
'Straight', as Jarvis uses it, tends to have a meaning more like 'square', or otherwise un-groovy. 'it must be great to be straight', in this context, would refer to his envying the security that she feels, now that her life has become more dull and routine after settling down.