Well, at least Wen conceals her emotions poorly enough that Rebecca can read her, closing some of the subtext communication gap.
Her having a slightly injured pride is workable. Even good, perhaps, because a starting frame of an exchange of favors is better foundation for a working relationship than just descending from on high as a saviour.
She's not entirely sure how to interpret the "tie of fate": it could be asking of she thinks their meeting was fated, or it could be asking if she thinks they are now bound together by fate.
"It is reasonable if you feel this as a slight against you," she says, "I would normally have asked for permission, but I did not know enough about this world to know if the leader of the demonic practitioner was powerful enough to hurt me, or if his technique was something I would be vulnerable to. I saw you were able to defy his powers, and that you and the town were in danger, and I did not have the time or words to negotiate an agreement, so I chose to act first and ask forgiveness later. For this, I consider myself to owe a favor to you."
A pause to let that sink in.
"If you wish, you may take that as the end of it: you can bank the favor for later, or ask something of me now if it is within my power and does not go against my dao*. However, if you would provide me pointers on this world and its ways, or instruct me in using the abilities I so rudely copied from you, I would consider myself further in your debt. I will not be offended if you refuse part or all of that request."
* Literally "way", Rebecca here referencing the principles by which a martial hero of ancient China lives. It is the only meaning she is aware of.
A local guide who is weaker than her but still of a relevant power level, worldly and not well-connected, and with a bond of battle, is ideal. She's hoping that's what she has here.