BM asking for money!

The mother of my husband's kids doesn't do right with the money she is granted for the kids. She doesn't work and lives with family members so she doesn't have any bills other than her phone bill. She recently put my husband on child support and he was ordered to pay $400 per month (just for one of the kids) but the court stated he doesn't have to start paying right now due to some flaws they found in the cs application she filled out. So they are doing an investigation and he is waiting for his next court date to find out the outcome of the child support. She gets an $800 disability check for one of their kids so she is wanting for anything. So two weeks ago she asked my husband for money for pampers. My husband told her no b/c she needs to learn how to budget the $800 she gets. We have both told her numerous times how we are not the ATM, how she needs to get a job, and how she should always buy the kids what they need first out of the $800 so she won't have to worry about begging for money. But she refuses to listen. Every month we get the same story about how she needs money for the kids after shes spent the $800 on getting her hair, nails, and partying with it. This weekend she asked my husband for $25 for pampers on FB. I found out the reason she needed the $25 is b/c she spent the last bit of her money on going to the movies with her friends to see the Purge instead of buying pampers her first priority. So I deleted the message before my husband saw it. Am I wrong? I just feel like she needs to grow up and be an adult. She wants my husband to take care of their kids and her expenses as well. I feel like If she wants to go out then she needs to get a job, but until then, the $800 she gets per month should only be spent on the kids. They are babies and right now they don't need much except pampers and food. I don't understand why she can't at least take $400 out and stock up on pampers, wipes, food to last her a month and spend the rest in herself instead of doing the opposite and then begging for money for the kids. I've talked to my husband about it and we're seriously thinking about getting a lawyer and fighting for custody. Its just ridiculous at how she blows money and is now trying to get child support as well. I guess she wants the $800 for herself and child support for the kids..but she needs a damn job. I just hope that when we do fight for custody that we win. I know the courts like to favor the moms most but she is so unfit and have her priorities so backwards that its a crying shame! So am I wrong for deleting messages she sends my husband? We're both tired of her begging and he ignores her most of the time anyway. I just don't want him giving in and feeling sorry for her ....because she needs to grow up, and work like everybody else since she wants to live like the Jones's! I also don't want it to look bad in court if she tries to play the victim and act like we don't help provide for the kids because we do. My husband buys pampers, and new clothes for the kids almost every week. We just choose to keep what we buy at our house since she's so irresponsible. Every now and then we will send them bk to her with a new outfit and a box of pampers but we mostly keep their new stuff with us for when they come here. We just don't believe in giving her money or helping her out when the kids don't have what they need because of her own fault. We told her she needs to ask someone else for the money or get a job. Are we wrong for how we do? ***Only comment if you've been in a situation like this or have good advice. We don't want any of the "I think your wrong, or he still needs to provide for his responsibility" comments if you can't relate to this.