Well, the obvious problems are
1. If the battery is any way doggy, it is being asked to start the aircraft twice without much of a chance to recharge. Shouldn't be a problem with a decent battery, but if the battery is decent, then there is no need to be worried about getting it to start
2. Some engines (usually fuel injected, which obviously isn't your case) don't like starting when hot....so not much point in getting one of these too hot!
Personally I wouldn't be bothered. If you have problems, explain them to your passenger, and explain why it isn't dangerous, and what redundancy is involved etc. As your said, she was a bit nervious because she didn't understand the issues involved.
dp