Mabruk! That's great news, masha Allah. May Allah help her on her journey. What you can do to help is to make yourself available if she just wants to talk, wants advice, or has questions. Also maybe check up on her every now and then to see how she is doing. (Or find someone who will be able to do that.)
The advice I usually give to someone who converts is to move gradually, work on the priorities (salah, tawhid, strengthen your faith, etc) and take things only at a pace that they can handle. She may not have this problem where you are, but a lot of times when someone converts, other Muslims bombard them halal/ haram or just random, unnecessary things. (For example, some well-meaning people will even insist that they should change their name to _____ ). So they should be prepared for that and not feel overwhelmed, but to build gradually. And never stop
asking Allah to guide them and help them along.
The other advice I generally give is that they will be tested. Just about everyone that I have seen convert to Islam has endured a very
heavy trial soon after becoming a Muslim, whether it is dealing with family, or an illness, or work, etc. So I tell them to be prepared for it, and when it happens to put their full faith in Allah, and He will help them through the other side. It is just a test. Allah tests the believers, but if they hold firmly to their faith and exhibit beautiful patience, they will insha Allah be put in a better situation than they were before.
Hope this helps!