Many people with phlebitis need to be on a blood thinner for life. Some pople only need it for a few months after a clot. If she was told she needs it for life she must make some arrangements to get the health care she needs.If a blood clot forms in the leg, it can break off and go through the body-generally to the lungs and cause a pulmonary embolism. That can be a life threatening condition. Most hospitals have medical clinics which can be more flexible for people who cannot afford medical care. Some counties have federally funded clinics which can help also.
About the twitching, this is not related to the phlebitis. It could be seizure activity or muscle problems or even a brain problem. She needs to have some testing done and possibly see a neurologist. Again, you need to find a doctor who will work with you even without the copay or a clinic. Something is definitely not right and she needs medical attention.