Worried about elderly Chihuahua

Hello, so I've had a Chihuahua for all I can remember, and she's about 14 now. I'm really worried about her health as she is a bit overweight even though she doesn't eat much, (though to be fair, she went through labor several times) she has lost teeth and is losing eye sight. I'm very worried that she's going to pass away soon. Is there anything I can do to prevent it, and if not, how do I stop worrying about it and cope with it when it happens?