My dog won't let me trim her nails.?

I have a (almost) 6 year old Bet Hound who for some reason won't let us (me and my mom) trim her nails anymore. She had no problem with it before. If we try she will growl than try to bite us. She is usually very sweet and mellow. If we even touch her nail she will jerk her paw away. We let her lay/sit how she pleases when we trim her nails but she won't tolerate it! We have to end up muzzling her with show tie (we unfortunately can't afford a mussel for her) (We don't tie it tightly!) It's been awhile since we trimmed her nails, She is basically walking on them now and it breaks my heart! They are VERY long and they are curling towards her foot. I can't stand to see her like this. My mom won't let us try giving her a bath than trimming her nails since it is in the 30s everyday and it takes forever for her to dry off. We have a slandered dog clipper, made for all sizes. Is there anyway to calm her? We can't afford the vet and yes, we do try using treats during the process. PLEASE help! She is my baby girl, it kills me to see her like this!