It's important to remember that every individual and situation is unique, and there could be various reasons for her expressing that she's too stressed out to worry about another person.
Stress is a real emotion that can affect people in different ways, and it's possible that she genuinely feels overwhelmed by various aspects of her life. In this case, it may not necessarily be an excuse, but a genuine expression of her current emotional state.
However, it's also possible that this statement could be a way to communicate that she's not ready for a deeper commitment or relationship at this time. It could be her way of expressing that she needs some space or time to focus on herself, her personal issues, or other priorities in her life.
In any case, it's essential to communicate openly and honestly with each other about your feelings and expectations. If her statement has left you feeling uncertain about the future of your relationship, it might be a good idea to have a conversation with her to better understand her perspective and see if there is a way to support each other during stressful times.
Remember that a healthy relationship involves mutual understanding, empathy, and the ability to navigate challenges together. If you both have different needs and priorities, it's important to address them openly and decide what's best for both of you moving forward.