What’s the best way to deal with the ex?

My husband’s has a 5 yr old daughter with his ex gf and we’ve had lots of problems with her but we try not to complain because it does nobody any good. My stepdaughter especially. We pay child support to the mother weekly but we’re also always sending extras along too. I always send gifts to my stepdaughter when I hear she did good at daycare or when she’s done well in speech therapy. When my stepdaughter comes to visit us, her mother NEVER packs enough clothes for her. She also never packs clothes that are weather appropriate nor does she pack anything that fits my stepdaughter. We don’t say things too often because again, pick and choose your battles. We do request weather appropriate because sometimes the temp will drop and it gets to be a little chilly. Last time my stepdaughter was here for a weekend the weather was cool. We asked her Mom to pack some warmer clothes, jeans and sweatshirts. She packed neither. I had to go out and buy clothes for my stepdaughter to wear.