Need help fast, my little girl is constipated!

I am in need of some help fast! My little Chihuahua was spayed on Monday. She is now constipated. She screams so loud that it upsets her mother, big sister and her brother and of course me. I've called my vet and he suggested using hairball remedy when I asked if it would be ok to give her mineral oil. Oh she does not like the hairball remedy! I have massaged her little tummy, given her water, kept her wrapped in her favorite blankie. She just looks at me with those little sad eyes and you can tell she is hurting. She weighs 1lb 8oz she is 18 months old so I can't give her too much of something. I would be ever so grateful if anyone has any ideas on how I can help her. She is breaking my heart! Thank you in advance for the help.

Are you sure it's constipation? So soon after a spay, I'd be worried about an internal infection or a UTI. If it truly is constipation though, feed her lots of pumpkin (canned pumpikin, not the pie filling, but pure 100% pumpkin). It is awesome. It firms up poops for diahrrea, and loosens poop for constipation. Good luck!

Thank you for the advice! I am going first thing in the morning and getting a can of 100% pumpkin. I have to try something. Yes, I'm sure it's constipation. I've been watching her when I take her out to do "her thing." I'll let you know how she does. Again thank you.