The way I read the OP, there are a total of 4 people in the apartment, three of whom probably shouldn't be there. Person A is on the lease. Persons B, C and D are not. The OP is Person D and has lived in the apartment for 3 years, apparently as some sort of guest.
The rent has not been paid in 2 months. I would assume that's Person A's responsibility. Since Persons B, C and D aren't on the lease, I'd imagine they aren't legally responsible for the rent payment.
The landlord has asked Person D to leave but has given no reason. The landlord has NOT asked Persons B and C to leave. From the facts presented, it looks like the landlord has not even asked Person A to leave.
Just Person D. Person D has another friend (girlfriend) who also lives in the building. Landlord has said to Person D, no, you can't move in with your girlfriend. YOU, Person D, are not wanted in this building, period.
That's why Person D is asking whether this is some sort of discrimination.
From the facts presented in the OP, I have no idea what discrimination basis Person D is claiming. Race? Gender? Sexual orientation? Age? I think Person D wants clarification as to why s/he was singled out and asked to leave whereas Persons B and C weren't and thinking perhaps discrimination played some part.
Of course, I could be reading the whole original post incorrectly
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