Question regarding sudden discoloration.

Out of nowhere my girl has this pink discoloration on her upper lip. Any idea what it may be and if so will it go away on its own? She got a spay and gastropexy done almost 3 weeks ago, went to the vet a few days ago for a check up and this hadn’t appeared yet.

Hello.  If I've got this right, your girl was in for a routine spey (and preventative gasteropexy), got through the post-op checks with no problems and then, days later, developed a couple of 'discoloured' areas to the front of her upper (maxillary) lip.  It seems to have been a long time since the operation, so I would have expected any temporary marks from the tube etc to be fading rather worsening at this stage, unless being repeatedly rubbed or  licked. This is rare in any case, and it wouldn't be a typical site for a tube to catch or rub. I am unable to see the picture particularly clearly on my small screen;  you say that the discolouration is pink, which makes it sound as though inflammation to an area of black skin is likely.  It's worth mentioning however, that actual loss of the black pigmentation to the nose or lips in particular, could be a sign of cancer or an autoimmune or hormonal change.  This is unlikely but would be particularly important to present to your vet. However, assuming the reddening or inflammation of the lips-skin, there could be many explanations for it.  These may include rubbing of the lips, over-licking (perhaps due to pain or the stress of the operation), or rubbing of the nose on a new surface or cage front, the friction of which may have damaged the skin and predisposed to excessive licking.   If removal of retained teeth happened at the same time, that may also be implicated. Ringworm is also more common when a dogs' immune system is down, which could be expected at the time of an operation, so will need to be ruled in or out (be aware that if it was Ringworm then humans - particularly those with poor immune systems - could catch it). There are also some unusual but potentially severe possibilities such as ulcers secondary to underlying disease, which might be exacerbated by the op. Therefore, there are some treatable problems that might benefit hugely from vet seeing your dog again.  I know that it may feel as though you live at the vets' at the moment, but another appointment to get the lip checked would be a good idea. The emergency vet (I assume that its also night time where you are) may help by triaging the situation.