Add a sewage ejector pit to the basement?

My mom rents our basement and it had a very small half bath. She wants to renovate and add a full bathroom. Our drain stack does not have avaliable space and is not deep enough underground to add to it. The plumber suggested an ejector pit. We have a few where I work and we avoid those areas due to the smell.

Is smell going to be an issue for us? It would mainly just be her using the bathroom.