New kitten

So I adopted another kitten (Remus, Male, 3 months, neuteted) for Michi (Female, 4 months, not spayed yet) for company since I feel bad for leaving her all the time due to school. So I did some research search and did what I was told which was keeping them apart and Remus in a separate room and I also put a towel under their food bowls with their scent. At first, Michi was calm and hissed everytime she was in front of Remus’s room. She did that for a few days and there was no hissing at all. Remus was fine when he ate with the wash cloth and so was Michi. They also played under the door and eventually we cracked the door open a little. Still no hissing whatsoever and the next day we just opened the door and let Michi wander in to his room. They seemed fine but Michi seemed a bit scared cause her tail was puffed up and Remus was good. Mainly Michi chased Remus around and she just kept swiping and pouncing which eventually lead to Remus to do the same that caused a few hisses from both of them and a few I guess monkey noises from Michi(??). My boyfriend and I also tried to distract them from Eachother but it didn’t work. We tried to grab Michi and she would just swipe hiss bite and did the monkey noises at us. In the end, we had to separate the both of them since we didn’t want them to get hurt. This was all in one week and we also let them into each other’s room. Remus was normal but Michi was cautious and slow.So we decided to do the process again but I decided to swap beds; they both slept on the beds with no hesitation. They would play with Eachother under the door and even laid on their backs while playing. No hissing!!!? It was another week before we let them see each other and it was the same outcome.. Please help, I just don’t want Michi to be lonely.. We were thinking that because Michi isn’t spayed, she’s freaking out and aggressive because Remus just minds his own business unless provoked.. We’re going to get her spayed in a few says to see if it gets better…