That is basically it. She recovers but then falls ill again, often with a cold or flu. She has several basic diseases that cannot be entirely cured by medicine but she can live with them. I pray that she can have a more normal life, do some sports and go to church meetings. That she will no longer need to stay alone at home. In Jesus name.

No, I don't agree with the words which describe their situation about sickness. Our words are powerful (Proverbs 18:21) and therefore is important to declare positive words and words of life.
Is she born again Christian ? Is she baptized in water as born again Christian ? Then is important to be free from any legal right from any unclean spirit. I know a brother who many times having victory against flu. How ? Decreeing in Jesus Name for example verse against any unclean spirit flu which is against him. And also declaring in Jesus Name any unclean spirit flu which is against him is bound.
For example Psalms 18:14 and Psalms 17:13 :
In Jesus Name I decree Psalms 18:14 against any unclean spirit flu which is against me.
It is working for him and can work for born again Christian who take a step of faith and believe Job 22:28 KJV, Revelation 1:6 KJV.
Lord in Jesus Name I pray to help this person who had sickness so many times to know The Truth and to be free because is written John 8:32.
For this person I pray :

In Jesus Name I pray mercy, grace, favor over this person. In Jesus Name I decree and declare Psalms 118:25 and abundantly life over this person. In Jesus Name I decree and declare what is impossible with people is possible with God over this person.
In Jesus Name I decree and declare 1 John 3:8 b) over this person. In Jesus Name I decree and declare "The Son of God came to destroy the works of the devil" over this person. In Jesus Name I decree and declare Zechariah 4:7 against any mountain which is against this person.

Lord's children are called kings first in Revelation 1:6 KJV. Is important to use authority and office of the king in spiritual realm. Also according with Exodus 20:5 is important to be free from any legal right from any unclean spirit.
In Jesus Name I decree and declare Exodus 14:14 and Deuteronomy 28:6-8 and 1 Chronicles 4:10 and Psalms 1:3 and Psalms 5:12 and Psalms 18:29 and Psalms 18:39 and Psalms 23 and Psalms 91 and Psalms 103:3 and Psalms 107:20 and Psalms 118:17 and Psalms 121:2 and 1 Peter 2:24 and Isaiah 54:17 and Ephesians 3:20 and Romans 8:37 and Philippians 4:13 and Luke 18:27 and Jeremiah 29:11 and 2 Samuel 22:33 and John 16:24 and according with Lord's will over this person.
Thank You Lord