It means that to visit him, his sister must drive a significant distance from her own home. It doesn’t give any indication of how far away she lives, although the phrase usually carries a suggestion of understatement, so a “bit of a drive” is probably quite a long one.''As you know, I live on my own and once a week my sister comes over. Bit of a drive for her, but she brings the shopping.''
What is the meaning of ''bit of a drive for her'' here? Is it like '' Driving is a bit of a problem for her''?
Thank you for your helps!