If you feel strongly called to write and you are writing from a healthy place, you will chisel out time somewhere. Like Smiley said, every writer has a thousand and one reasons to postpone committing words to paper. Many if not most of those reasons are only tangentially about time.
I get that you feel like this would be in some wise payback for her former support of your projects. That's good of you. But it would be, IMHO, a huge mistake to sacrifice your GAL activities to her ambitions *at this point*. Watch her and see what happens. Is she willing to sacrifice some of her outside activities for her writing? Is she willing to sacrifice sleep? If so, then step up. You're now a collaborator (in the positive sense of that word) and a supportive partner.
If not, you're just a martyr. Whether you want to or not, you will probably find yourself monitoring how she uses her time; bad. If she is not using it "wisely", you will undoubtedly feel resentment and may be moved to comment. Double bad. Save yourself the drama. JMHO, as a writer with a million and one excuses.
"Show me a completely smooth operation and I'll show you someone who's covering mistakes. Real boats rock." -- Frank Herbert