While I understand being on a fixed income and you have the money set for this, that and the other thing, I do think that one is allowed and "allowance" or "pin money" to with what they want (within reason.) If you have an interest or hobby and you've set yourself up with a budget for how much you can spend on that interest or hobby, then why the guilt? Save the guilt for if and when you go over your budget, are you not entitled to something for yourself?
I get concerned about my own spending simply because in my first marriage and for the majority of my adult life, I was really bad with money...I'm not now. My spending habits in my first marriage were one of many reasons my marriage failed...for that I feel guilty. But I live a different life now, and I have an allowance plus money from a small business, so I'm working to "live" within the confines of my allowance...I really only feel guilt if over spent my checking account, which I'm happy to say, doesn't happen now, or at the very least, maybe happens once a year...
Our needs are met, we're basically living within our means, our bills are paid on time...and for the first time in well over 20 years, I got my credit score and it's more than favorable. So there's no need for undue guilt.
I did say to my husband this morning that one of the reasons that I've been slow to start my business or even grow my business is that I worry about 'wasting" money if the business is a failure...and my husband said, "your business is also your hobby, it makes you happy, so the money's not a waste..." so no reason for guilt.
It doesn't sound to me like you're wasting money, it doesn't sound like you're spending money to the point that creditors are hounding you to pay past due accounts...so please, if you're allowing yourself a small pleasure a week, a month, or whatever, banish the guilt...there is nothing to be guilty about.