Well That’s Fantastic
To assume that parents can be this innocent in the 21st century is such a nice feeling, just like this mom here who knew nothing about new-world slang. She used WTF for “well that’s fantastic” to show her happiness over her daughter’s grade.
Perhaps she knew what WTF meant but was intentionally joking with her daughter to congratulate her on her brilliant chemistry result. And if she really didn’t know what she was saying, it means there is a whole community out there using these terms wrong.