What do I do beside this lonely cat?

I have had two cats for a long time...one male, one feminine. The male was diagnosed with kidney stones give or take a few 2 weeks ago and I put him to sleep. Now my female is bored, im guessing, and she constantly follows me around. I feel bad because I didnt approaching her as much as the male and I dont pay much attention to her...what should i do? get another cat to maintain her company or what?
Yes, your cat is lonely and in a state. She has recently lost her playmate of many years. She desires you to give her the attention she's missing. Whether you like her smaller amount is not important. Try giving her some more attention or get her a new playmate. They are tons older cats at no kill shelters that would love a new domestic and playmate. Give it a try.
Were the kidney stones fixable? Two of mine hold had them and neither of them came close to needing to be euthenized over it.

If you hold no love to offer your cat, find her a better home. It makes no sense to own an animal as a pet when you don't care if they are grieving over missing friends or not.
Answers:    I don't believe she is bored, I think she is looking to you to take place of the comfort she have when her buddy was alive. I'm not sure introducing a new cat would be prudent right absent, as cats introduced as adults don't always work out. I would just give her additional attention, maybe some new toys, and some extra snacks.
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