If the 150 is too much and a train can take you part way why not try that? Not sure if you can store a tandem on a bus but if you can then that would be a second option. Or maybe your family can meet you part way.

One other thought is have her ride as far as she is comfortable and then catch the bus the rest of the way and you can solo the tandem the last bit. I have, and know of others who solo a tandem sometimes.

Sometimes you just have to adapt if you really want to do something.