do you think an absent mother has a right to dictate how often she has visitation

The title is confusing. My husbands ex partner is constantly running away from home, going on holidays without notifying anyone (doesnt take a phone) and because she is a methamphetamine user her own family have reported her to police as missing in fear shes been murdered. Shes almost 30 i thought is worth mentioning. My husband and I care for kids on a full time basis ever since her last little episode of running away for 3 weeks. It used to be 50/50. We now allow the kids to see their grandparents nearly every afternoon and their Mother every second weekend until we can get court orders in place. She must have run out of money or has come down from her drug high and contacted my husband for the first time in 4 weeks (hasnt even asked how the kids are in 3 weeks) and has said "this arrangement" doesnt work for her. that she is upset we took the kids and are giving her only weekend access. The kids have come on really well, we have them in a routine, theyre eating real food, getting sent to school with food (something the teachers have said she wasnt doing and they gave the kids food from the staff room) and their behaviour has improved at home and school. My 10 year old step daughter wets the bed every single time she goes to her mothers and on the first night back at ours she does but hasnt wet in weeks. the kids have begged to stay with us. do you think the mother even has a right to say what she wants when shes either not around and is leaving the kids on their own or relatives... the children are a meal cheque to her.