Question about my female and weight gain

I've had my 2004 female snow motley corn since January of last year. When she came in to my care she weighed around 75grams and was 4 feet long...It was awful :/ With regular feeding I got her back to a healthy weight and I was feeding her an appropriately sized mouse or rat every 10-14 days. A month or two ago I noticed She was at about 325 grams (I don't weigh her as often as I do my BP's). This week, she was over 380 grams! I haven't changed her husbandry or feeding schedule at all...

Is this weight gain part of the normal breeding cycle for a female corn? I'm sorry if this seems like a silly question, but I don't know anything about the breeding of corns so I just want to know if this is normal.

I also noticed that the last third of her body looks like she bigger, and feels a little more solid than she normally does. She is my only corn and has not been paired with a male...

I just want some clarity so I'm not completely clueless as to what is going on with one of my snakes :) I can post pictures or a video later if you would like! Just let me know. :)

The first concern I'd have is if she'd defecating. If she is, then it may just be her bulking up. My female does that sometimes whether or not she's laying. At that length, she should be over 400 grams and from what you said, she's been putting on weight since you got her. That's a good thing. It is also possible that she has eggs (they don't need to be bred to have that happen) and it seems they gain more while gravid. It's about that time of year.

She is a pooping machine! So I don't think that is the problem :)

Over 400 grams?! Alrighty. So I shouldn't have anything to worry about? Should I keep her on the same feeding schedule or feed more frequently?

Since this is breeding season and you never know if she's going to lay or not (at least my corn never gives me an indication one way or the other) then I'd have her on an every 7 day feeding routine. Also, to give you an idea of how much my girl eats, she gets 2-4 (depending on whether or not my male decides to eat) adult mice this time of year. The reason it's so many is because I haven't tried switching her over to rats and the mice she's getting now are small/medium. She's not fat and when she lays, she tends to drop down into the 300's range but then that helps her bulk back up. You want to make sure your girl isn't getting fat, but that she's a good healthy weight. As a 2004, she's no longer growing so you can adjust the feeding to keep her at a nice even weight. Around August, I drop down to 1-2 mice per week and then over the winter, the schedule gets pushed back to an every 14 day feeding schedule since I don't fully brumate them but they are less active. Just trust yourself to know your snake. Unlike bp's, corns have a tendency to eat anything and everything so you can take your time getting weight on her. Chances are, she's just filling out and with corns, it can be harder to notice than on some other species because they don't get that pudgy look that bp's and such can get. Since you have a female, be careful not to allow her to get too fat as they have a higher tendency to eggbind when that happens.
As of this morning, I weighed Kitai empty and she's sitting at 496 g. It's also possible that some of that is egg weight since she was bred this year but she has a tendency to lay in June/July time frame. After laying last year, she'd dropped to 338 g. She'd been sitting around 450 but had skipped 2 feedings right before laying. She's also 11 y/o so not sure if that will matter much or not. Kitai's been this size since she was about 4-5 years old.

What Dracoluna said! My girl is a 2006 and she weighs about 550g right now. And I feed her every 7-10 days. Every few weeks I'll skip a meal just so she's not getting too pudgy.

Great job on getting her back up to a healthy weight. I wouldn't worry to much about the weight gain. It could just be this time of year, they tend to simply gain more weight in preparation for breeding, or it could be that she's retaining a little poo and took a large drink of water right before you put her on the scale. As long as she's pooping and the weight isn't going down, I wouldn't worry if its going up.