Americans are still showing up for mom this Mother's Day — but with more budgeting, bargain hunting and strategic splurging as "momflation" pushes up the cost of flowers, brunch and gifts.Why it matters: Mother's Day is becoming a snapshot of the modern U.S. consumer economy: Even as shoppers complain about inflation and rising prices, many are still willing to spend on special occasions — just more selectively.Americans appear increasingly will…