One teacher at my lo's IFC accidentally opened a new tin of formula milk. :( My lo has been on total bf/bm since 2 months plus. The tin of milk was bought just in case of insufficient bm. Should I let her do mixed feeding at IFC, cos it'll be a waste if I throw away the fm after 3 weeks, or should I just continue to let her drink bm?

I'll continue to let her drink bm. Between money and more nutritious milk, I'll choose more nutritious milk. If you want to try, you can attempt to sell it at a discounted price on Carousell, but no guarantees that there'll be takers.

if you have sufficient bm, then maybe you can give the formula away to other infants there? since ur LO is already on total bm/bf, I rather maintain it that way if possible.