Your Tamagotchi will not become an oldie until you stop taking good care of it. I had a Kuromametchi that took until age 24 (I think) before it finally became Ojitchi after I left him alone all day. By the same token, I had a Necktietchi who turned into an oldie at around age 5, because I was really busy and didn't take good care of him.
So if you want to try your luck and see if your Makiko gets married as an adult, keep taking very good care of her, and her years will advance, and you might eventually see the Date Place. If you want to see the date place ASAP, then you may want to let her change into an Otokitchi.
However, Makiko is a pretty cute character, and it's kind of sad to see her get old. :/