Worried about mums health?

My mums the type that frets and stresses things over and over and over. She often keeps so much inside and when she finally has had enough it's awful on her behalf. I can see that emotionally/mentally this is killing her and the physical symptoms are worse; she's literally withering away. The skin on her face is hanging onto her bones that's how much it's gotten out of hand, despite the fact shes very careful with her diet (no fat reduced salt intake etc). Her only support system is me and at times my sister, what more can I do to help her? This kills me seeing my mother like that the stress she's under, what can I do to help her get back on track both mental and physical? I've thought about taking her out on a surprise spa treatment but I'm still in high school and in year 12, it's going to be difficult arranging everything.