So, you are giving your colleague some of your research code to use on her own problem. If she ends up using, or trying to use it, then I predict two things.
(a) You will end up having to help her understand the code well enough to use it. This is very likely, amounting to practically a certainty.
(b) You will have to adapt the code to work on her problem. This is still very likely, but not quite as certain.
I'd say (b) definitely entitles you to co-authorship. (a) is not quite so clear. If you just give her the code and don't do anything else (in which case she is unlikely to be able to use the code) then you definitely aren't entitled to co-authorship.
Whatever you do, you could still be denied co-authorship. However, bear in mind that you cannot (in my opinion) reasonably withhold the code (that seems to me contrary to what research is about) but you are not required to work with your colleague on her problem for nothing. Therefore, if you do end up spending significant amounts of time working with your colleague on her problem, then bring up the issue of co-authorship early. If your colleague or her mentors don't want to give you co-authorship, then ask yourself why you would spend time working on this project.
You also say:
I'm prepared also to offer additional help with data pre/post-processing & writing.
This is a separate issue which I'm not addressing here. I have just focused on the involvement which will naturally stem from you providing your source code. If I understand your quote above correctly, this refers to optional assistance you are prepared to provide.