Feliway (stress reducing pheremone) sufficient for cat with weight & hair loss?

6 year old cat, been underweight for a year and has lost fur on her belly and back legs in past couple of months. Boyfriend suspects licking, I wonder if it’s illness.
History:
-Hemobartonella, when she was a couple years old.
-2 years ago she moved to my mom’s farm while I traveled for many months; she got a stress-induced “cold,” lost energy and appetite, medicine caused further loss of appetite, and she nearly died. Only an appetite stimulant from the pet store saved her.
-Moved 1,000 miles just over a year ago, into a new apartment with new boyfriend, plus introduced 2 cockatiels to the family. She is snooty around the birds (knows not to eat them but is resentful of the attention they get) and runs from the boyfriend half the time (even though he tries so hard, she only likes him part-time).

Have taken her to the vet twice over the past year about weight loss. The first time they told me she was in the normal range, but I knew she was thin compared to her norm. Now, she has lost even more weight, looks like an elderly cat, and started losing hair a few months ago. On visit #2, blood and thyroid checked out (thyroid just barely) and the suggestion was anti-anxiety treatments including a calming pheremone plug-in. We did not check urine or do a full panel because I didn’t have the money. The vet’s gut feeling was thyroid, but it was just barely in the acceptable range, so now she says stress.

Besides the birds, Lucy doesn’t seem unhappy. She has lots of property to hunt on and I still spoil her. I am transitioning off indoor formula food since she’s outdoors again, and I’ve even been mixing that appetite stimulant into canned food. She gets all her flea/tick/worm meds. Still skinny & half naked.

Have you ever used Feliway or anti-anxiety meds on cats? Do you think the vet has been thorough enough?