It could still have been a brutal rape within a relationship.
However we know TLR is a manipulative, violent psychopath who lies and rewrites history. He claims to love Ryan but poured petrol on him in an attempt to murder a small child in a horrific and painful way.
He claimed to love his mother and to be devastated by her murder but we saw him treat her dreadfully and be violent towards her.
It is entirely in character for him to have brutally raped Becky whether they were in a relationship or not. It is in character for him to have rewritten history on that point.
Becky told her Mother it was rape. She killed herself due to the distress. We have no reason to disbelieve her about something so important to her and her baby.