This was an interesting chapter.
Momo is really confused and her questions about Riko's intentions are something that she should have considered before asking for Riko's services again(now that she knows Riko might be Aoi, her student, therefore something that might screw up her carrer). However, she is completely mistaken if she thinks that highly of herself.
Like, Riko is a sex worker, it doesn't matter her reasons for doing what she does. It's not like she is closer to Riko than any of her clients, not to mention, Aoi might not want to interact with a client while she isn't doing her work - which is not only understandeable, but also wiser.
Right now, even if Momo wanted to keep seeing and meeting up with Riko, it's quite foolish to try interacting with her while she is Aoi. Not only its arrogant to think she is special over all of Riko's clients but also, it could allow others around her to find out what is happening.
I get that Momo is in love or something similar, that love(specially the first love) makes us weird things, and that she has no previous experiences in these situations to help her deal with everything as a rational adult, but dear God... At least take a deep breath and do not jump into conclusions.
All in one, the next chapter could lead into some interesting developments. I wonder what is going on Riko's/Aoi's head.
And the sister... I predict she will not only ask akward questions but also will notice how Momo is acting differently. I wonder if she will find out what is going on and if she will berate her older sibling.