Can my husband's ex wife get more money in child support after changing jurisdictions?

My husband and his ex wife were divorced in Arizona in 2011. Since then she has moved (with their daughter) to Pennsylvania. Last week my husband got a letter in the mail stating that his ex wife requested a stop payment on his child support in Arizona. when he asked her about it, she said that she was trying to get under PA jurisdiction. We think she did this in an attempt to get more child support. Is that possible? If she feels she needs more money can my husband succeed in gaining primary custody since she is struggling even with the current amount he pays?