unsure if hamsters are squabbling, fighting, or play fighting

[TheRobotHammies]

hello! i recently made a post in the introductions, but i really only joined because some of my hamsters' behavior has me a little worried. i'm a very, very new hamster owner with a lot of worry and questions.
please forgive me if this drags on for a while, i just wanna give as many details as i can.

i have two female roborovski dwarf hamsters (Lilith and Ava) bought as a pair and have lived together since birth. at the time of writing this, i've had them for nine or ten days as a gift from my parents. it was a very unexpected gift, and with no prior preparation since they wanted to surprise me (which is nice and all but they could've been a little more prepared :(

i've had them for ten days now and have been getting along perfectly well. eating from the same bowl, running in the wheel together, and sleeping together.
about three days ago, i noticed Ava acting (as best as i can describe) aggressively towards Lilith? i looked up what they could've been doing, and from what i read they were just squabbling (squeaking, one holding the other down to groom, etc). they did it multiple times the first day, but what worried me was them appearing to me wrestling. they always stopped after just a few seconds and Lilith would lie on her back for a bit until Ava left. what worried me the most is Ava scaring Lilith away from the wheel to the point she jumps off ledges in the cage (i'll describe their cage in a bit). this happened a few times, even in their house where they sleep. but the morning after, i saw them sleeping together again.

the next day, they went back to how they were before. eating and sleeping together, and being around each other peacefully. but lilith didn't run in the wheel as much. and at some point, Ava did start that squabble thing again, but it was extremely brief and they didn't do it for the rest of the night. and again they were sleeping together the next morning.
i also added a new wheel in the cage so they'd stop trying to run in just one and possibly fight over it. it's worked pretty well so far and both hammies run in seperate wheels. one hamster would run in the other wheel if the other hamster wasn't using it or not looking, but always returned to the other wheel.

Today, they've started squabbling/play fighting again. they only did it a few times (about three maybe) but i didn't hear any squeaking. i don't know if no squeaking is normal in squabbling though. they still went on about their activities afterwards though.
at the time of writing this, Lilith has not left the side of the new wheel i added. she also seems to avoid Ava whenever she approaches. earlier they were together and Lilith went behind Ava while she was eating and peeked out at me. she didn't try stealing Ava's food or anything, only sniffing what was on the ground around her. but when Ava did finish eating, she seemed to jump on Lilith and pinned her down, only to go back to a wheel and start running. Lilith layed on her back for a bit but got up a few seconds later and groomed herself again.
for the whole night so far, Lilith has stayed near her wheel and run in it. she also seemed to be asleep by her wheel and not with Ava in their little house. she almost always flinches or runs away when Ava sniffs her, and when she tries to sniff or interact with Ava or when they both interact with each other, Ava almost always starts acting out again, but sometimes she doesn't and leaves Lilith alone. these moments are very brief and sometimes Ava chases Lilith, but never for long and always does something else.

i'm almost certain they're acting like this because of their enclosure. i don't know the exact measurements, but to me it looks like there's more height than width, and there's two upper floors which is also where each wheel is on. Lilith stays on the very top floor while Ava stays on the second and bottom floors. there's one food bowl at the bottom and two bottles on either side of the cage on different floors. there's about only 1 1/2 or 2 inches of bedding because the bottom part is too short to hold more, and less than an inch of bedding on the upper floors. they don't have a lot of space to run freely so they mostly run in their wheels or crawls through tubes i made for them out of a paper towel roll.

i asked my parents to consider getting them a bigger cage or an aquarium so they have more space to run around, for toys, and two of everything. my mom said they're fine with what they have and said to let my dad do the searching for a new cage instead, and that if i wanted to get them a new cage i'd have to buy it myself. i am a minor and still live with my parents and have yet to find a job because of social anxiety. i do have money saved up but i doubt it'll be enough to afford an enclosure. we also just can't afford one right now since money is tight (i told you we were extremely unprepared!)
i expressed my concerns to my mom and she told me to stop being sensitive about this. she offered her fish's old tank for the hamsters and said she wouldn't mind them moving in, but i'd feel bad about taking it since it's all she has to remember her fish but i might just end up using it if we can't find a good enclosure within our budget. i don't wanna have to seperate them not because i want them to live together, but because the only other enclosures i have for them is the petsmart box (i know this company sucks but it's the cheapest we can afford) and another old, (possibly) smaller cage that i don't have space for in my room.

i'm so sorry for rambling for so long. i just want to know if my hamsters are only squabbling, play fighting, or actually fighting. Lilith just seems to be acting afraid of Ava, and i don't know if that's normal after squabbling. sometimes when they're near each other all they do is greet and sniff each other, and i never see any of them bleeding or injured (unless one gets scared/pushed and falls off the ledge) so i'm hoping this is just play fighting or squabbling.
i've been keeping a very close eye on them since i have a wonky sleep schedule and have basically become nocturnal just like them. i just want some answers please.