Whistling sound--does this warrant a vet visit?

Hi everyone! I'm new to the site. I've had my ball python Mellie since May. She is five years old-- I adopted her from Craigslist. She has always been very healthy--she eats well, has full sheds and is docile and friendly.
Tonight while I was holding her I heard what I can only describe as a "whistle" sound from her nose. It was pretty quiet, and I heard it around 4-5 times. I think she eventually stopped. She is back in her enclosure now, and I haven't heard the whistle--however, it might be because the sound is too quiet for me to hear.
She has no other signs of illness--she doesn't have any discharge and she ate a rat on Sunday. Her behavior is normal as well.
Do you think this whistle warrants a vet visit? Mellie's last shed was approximately one month and one week ago. I am so afraid she might have a respiratory infection. I do not have much money at all and it would be a huge financial strain, but she is worth it to me because I love her so much.
Thank you so much for the advice. I am so worried.

She may be going into shed. It's very common for BPs to who make whistling sounds in the days just before a shed. I wouldn't worry about it. Just keep an eye on her.

I think shed also, as long as your python isn't doing open mouth breathing, or doesn't have mucous from the nostrils, or mouth, which indicates RI.

Agreed that it is likely that she is going into shed as others have stated. Just monitor it for any other signs of an infection.

Huh.

I've heard snakes whistle RIGHT before they actually shed their skins, you know -after they've come out of blue and their skin is obviously loose and crinkly.

Now I'd love to know the physiological mechanism that results in a snake making a whistling noise out of its nares BEFORE any signs of ecdysis.

What some snakes do, however, is make a whistling noise when they are irritated or stressed. This is a function of air being expelled at greater force. It is very common. It is more common than hearing whistling noises immediately proceeding the actual physical act if shedding.