I usually make some sounds which show interest.Like oh!,come on,no way,I don't believe it or pity,everything happens to you,do you mean that...?,what did she say etc?
Generally it is good to caress her if she says sth positive and not kiss her while she complains.You should also not put your pen1s out while she talks about her problems.
SSSSAAARRRCCCAAASSSMMM!!!
You're redeemed!!
;)