the brand "Little Noses" makes for kids, nasal spray decongestant.
From drug stores.
Do not use a bulb syringe too much... it will abrade the inner nose. It being tender. Our Pediatrician always cautioned about that.
Make SURE... she does not get secondary infections.... as this age they can't spit out mucous... and it can affect the lungs.
I got Bronchitis that way once... from a head cold. My post nasal drip was then getting my lungs infected... and I got worse.
5 months... is a LONG time... is it the SAME cold???? I would check about that. She is so young....
Pertussis is also epidemic in some states... make sure, she chest does not get... affected...
I hope she is still feeding well? By breast or bottle? Not getting dehydrated???
I would maybe get a 2nd opinion, from a Pediatrician...
all the best,
Susan