A UTI would be my last guess as the cause for this happening. I suggest that she's just exploring herself. She's discovered another part of her anatomy. She may find touching herself pleasant or she may just be interested in what is down there.
My 2 yo granddaughter loves to take her diapers off and when it's time to put them back on will lay down, as she's asked, and then touch her vulva, the area visible on the outside, and the creases between her legs. She does the same at most diaper changes. So normal.
No need to worry about her getting a UTI. Touching/exploring rarely, if ever, causes one. Putting on the diaper too tight will not cause a UTI. Neither will not changing her often enough. Or taking a long hot bath. UTI's, tho they do happen, are not common at this age.
She doesn't have one now. If she did she'd cry when urinating.