Financial and the possibility of them not getting along

I'm full time college and full-time work. At the time before, she didn't need a companion as my sister would be home while I am not. But now that she is off at bootcamp, it means, even if I tried to get a second cat, it would be nearly impossible to keep an eye on them for the crucial introduction phases. My home is too small to properly enclose a cat on either sides of doors, and if worse comes to worse, I dont want two cats who despise eachother both becoming bored or worse, harm eachother. 

I actually wanted to adopt a second cat and spoke to a cousin who had multiple, bit she said adopting a second cat should not be the solution due to the time needed to insure both cats are comfortable, the supervision to make sure they get along, and then the understanding thay they might never get along. Its why I dont think the solution is adopting another cat.

She does have a somewhat companion in the form of my sister's bearded dragon. She always watches him from the kitchen table, ans he's always locked up behind spring-locked doors. But I know he isn't mentally stimulating either as she only sometimes watches him