Dazed and Confused

[Cadet]

You dont want to be in a relationship with her while she is in a relationship with someone else.

That is when saying the above might mean something.

Should I say this to her? Should I tell her I don't want to be in a relationship with her while she is in a relationship with someone else?

I understand what you're saying, but I don't at the same time.

Not right now,
is she asking to stay with you?

That is when you would say it.