@ineedadvicepls I know this is now an old comment, and it's quite likely you won't see my response, but I thought it may be worth replying anyway, for any others who may stumble across this thread in future who are wondering the same thing.
I believe I may have DID, I don't have any experience with getting support from loved ones. But I wanted to say, just the fact that you want to be a supportive, safe person for her will mean a lot to her.
It's hard for me to give any specific advice, due to my lack of experiences to draw from. Every person is different, and so the type of support they need will look different for each person. So communication will be important - it is okay to ask them directly how you can best support them.
Keep an open mind. If they feel comfortable sharing their experiences with you, listen and believe them. But don't push them to share if they aren't ready.
Also keep in mind that there may often be times when they need reassurance from you that they aren't a burden, that you still like them, and whether or not they have done something wrong. Due to the hardships I've endured, I often struggle with thoughts that I've done something wrong and made someone mad at me (which feels like the end of the world 😒), or that people are secretly thinking negative things about me. I believe this is common with emotional abuse victims to fear these types of things, and to feel like your needs aren't important. But as a disclaimer, this is just my struggle, and meant to function as a example, everyone is different.
Some of us also struggled in the past with the fear, of what other people think of our other alters, and whether their different way of acting or their very existence makes other people uncomfortable. So if other alters make themselves known to you, it can mean a lot to accept them and talk with them, just as you would normally, rather than refusing to interact with them or getting upset.
It can also be helpful to read on the four trauma responses (fight, flight, freeze, fawn), as it may help you recognise when they are triggered.
