How to tell my mom she’s getting worse..?

So my mom is really sick and has been for a long time. Part of it was this “lump” in her head which has been growing. She just found out it’s vascular dementia and she asked me when I went to see her if I thought she had gotten worse in her mental state. She went on vacation for 2 months so I hadn’t seen her and she asked me 4 days into seeing her so I hadn’t really had the chance to notice, so I said no. But since she asked, she has done several things that make me think she has gotten worse, but how do I tell her? It would break her to hear it 😞