My kitty has a sore...

Hi everyone. I'm really hoping someone can assist me before I can get my kitty to the vet. I won't be able to for a day or two and I'm going insane. Two days ago I noticed my kitty Layla had a slightly swollen area on her gums. Tonight I checked on her again (I check about twice a day since I saw this.) and this time there is a decent sized almost white-ish bump where the red sore/swollen area was.

Other than this, she is perfect. She's playful, loving, big time appetite (She is a growing girl, after all.) and is just her normal self. She's even rubbing her mouth on things to mark her scent like normal. She doesn't even seem to notice it's there. When I was looking her over I touched it and she was fine. And since she's rubbing that area on the walls and my hand, I'm going to assume it doesn't hurt her.

I'm still really worried about this though. I lost my best buddy (A cat I had since I was in my early teens.) to cancer last year, so this is too much for me to handle and I'm paranoid. (Her gums look nothing like his did though.)

Can anyone offer any help, or ideas as to what this could be? Cancer is my biggest fear, but the jist of what I've read so far suggests it could be Cancer, Rodent Ulcer, or even a dental issue. Any help at all would be greatly appreciated.

Maybe it's just abscess relating to her teeth or gums. Honestly, the best thing to do is meet with a vet.

How old is she? If she is 6 months or younger, she may be getting new teeth.

That is all I am hoping it is... I really can't lose this kitty. She means the world to me. And it's still too soon after my little buddy passed on. I did notice after looking at it again this morning, it doesn't look abscessed, just swollen. Is that a better sign at all?

Edit: just saw your post. She is just over 1 year now.