Anyone got pain in left breast?

Has she seen a doctor about this specific issue? If not, she should.

I understand the inclination to work on lymphatic drainage and on inflammation in general.

Hormonal fluctuations can cause breast pain. Sometimes people also get mammary cysts that resolve on their own but can hang around for a couple of cycles sometimes, and can hurt a lot. (Just so you know, cancerous growths usually do not cause pain.) If she has a history of hormonal contraception causing the same sort of pain, then I would assume hormones are again the cause.

Fluctuations in hormones are extremely common when someone has chronic illness, chronic stress, issues with cortisol, and any kind of HPA axis dysfunction. Also, what's normal hormonally for someone one year simply may not be what's normal anymore a year later, especially if you are trying different treatments and altering the body's chemistry constantly as you treat for chronic tick-borne infections.

I have had breast pain from hormonal changes, very painful breast cysts, HPA axis imbalances, very low hormone levels, and loads of changes to these systems over time. This all sounds very familiar to me.

You said her functional medicine doctor says the pain is coming from nearby cartilage. Does she doubt that's the case? Did the doctor mean rib cartilage (i.e. costochondritis)? (Lots of us here have costochondritis, too.) Can you describe what the pain is like - shooting, stabbing, worse when breathing, dull, like a bruise, a lump is present, swelling, heat, etc.?

She says the pain is dull but always there. It hurts more with any compression (like a bra), tender to touch. Kind of like a really bad bruise. If you press on it with fingers in specific spots the pain can be so bad it makes you want to pass out. Over her heart it feels like someone stabbed her in the heart and never removed the knife. No swelling. No heat.
Felt lumpy. Lady doc said there was fiber cystic tissue on the 9 oclock auxiliary line, but the pain over the heart is stably and tender, but the under arm pain is duller. She can not sleep on that side at all.

Thank you!