The '30 Days' singer, who is set to marry rugby star Ben Foden, said that the pair make sure not to frustrate Frankie Sandford, Mollie King and Vanessa White with talk of their weddings.
"We don't bother the other girls by talking about it all the time," she told OK. "We pull ourselves to the side and have a little chat about things.
"Neither of us are Bridezillas, we're just there for each other."
Healy also confirmed that the rest of The Saturdays will serve as bridesmaids at the "laid-back" ceremony.
"I don't want to stress too much, I just want the day to be a really nice, laid-back fun day," she said. "In my life right now it is probably the most stressed I have ever been.
"We could have put [the wedding] off until next summer but there would have been another rugby tour for Ben. We want to be husband and wife more than anything."
Healy gave birth to the couple's first child Aoife Belle in March.
Wiseman will marry Marvin Humes of JLS in July.
Watch The Saturdays in the video to '30 Days' below: