Miscarriage in 7th week

Hi everyone,
my cousin had a miscarriage in January. She is 42.
Hr father had died suddenly 1 year ago, she had the miscarriage a few weeks after the anniversary of his death. He had no health problems but suddenly got a heart attack, which was extremely traumatic for her. There also took place some stressful events with an ex-partner of her husband who learned about the pregnancy and made threats to him and my cousin, who got very stressed and angry by this.
The pregnancy was developing excellently until the miscarriage, according to the doctors. Menses returned exactly 1 month after the miscarriage and is punctual, no pain, no cramps. She and her husband want to have a baby very much, so they have started trying again.

Beyond vitamins and supplements, is there something she can do to boost fertility? Her homeopathic doctor told her she has no experience with fertility homeopathy protocols, so we are seeking advice elsewhere. My cousin too follows homeopathic advice for ailments since 2008, never smoked, never drank alcohol nor coffee, has no health issues.
Thank you.