I really feel the first way to get some to run like hell is to mention medication or anything like that. Originally it sounds like you were close or you wouldn't be asking.

. Depending on how far you live ask to go to curtain baby mile stones, first sonograms, sonogram that tells the sex, birth if she wants you too., first baby appointment, 6 week check up.

Text and call often, send random little care boxes ie. Mom's favorite candy ( just something small little extra that is just for her to enjoy because she'll forget about doing little stuff for herself) and a $1 baby thing.

If you here she's having trouble do something nice: one of my friend's called and you could hear my son wailing in pain from colic. It was a very short call. Later this small pizza shows up at my door because "I needed a break".

Look into what catholic charities has to offer. Remember fist she's your cousin, (some descriptive things she likes to do) then she's a parent (all the other things about her) lastly she has bipolar. To many people stop treating moms as individuals once they have kids and to many people put a persons mental health above the person.