They're so irritating, aren't they?
How many times is she taking 150ml? If it's 4 or more, that's probably enough to keep her going, depending on your milk powder - mine is 1L max per lamb per day, some are 1.5L max. If she doesn't look hollow, isn't hollering for a feed, and isn't becoming skin and bone, she's fine.
If you're still not happy, I wrote up some suggestions
here - have a look at that first.