I don't think it's weird , after all I'm assuming you're 'pro choice' not 'pro suicide'. There is nothing wrong with wanting your friend to live, wanting them to be happy and safe. I think it'd be more weird if you didn't care. It's kind of like if you had a terminally ill family member and you choose DNR. You don't want them to die, it still hurts like hell but you do it because you know they're in pain.
You can still support them and listen to them, if they allow you, without pushing them either way. If they messaged your other friend, it is possible they're undecided on ctb. If they still have some hope, then it's not hypocritical to help them explore alternative options, such as recovery support. For example, I believe suicide is my only option and also the only option for some people. But that's only because i've tried recovery and i know my situation won't change. BUT i also believe that for some people recovery is possible. I respect that for many of us, ctb is the logical answer but for others there are other answers.
I'm not saying push them into anything, support or otherwise. But if they're open to it, you can help them understand their options either way so they can make their decision. Some suicidal people do want someone to step in and help them. Maybe explore if your friend wants that first. You can offer that support without forcing it on them. E.g - asking do you want someone to listen or someone to help keep you safe from your thoughts or just someone to respect your choice etc.
If they're decided on ctb you can simultaneously respect their decision whilst also feeling hurt by it. We don't choose our feelings.