Chemical pregnancy or false positive?

I have a friend from work who’s been trying to get pregnant for the last few months. Here’s the run down of events over the past week:

Jan 1st- (12dpo) She took a test after feeling nauseas for a few days, got a faint but clear positive (I’ll post a picture in the comments) but that was in the afternoon so she took another test in the morning to see if it would be darker

Jan 2nd- (13 dpo) she didn’t pee enough on the test but still thought she saw a line after a minute or 2 and then it went away.

Jan 3rd- (14 dpo) she took 3 different tests. FRER, digital, and an internet cheapie that all had clear negatives.

Today- (17 dpo) now she’s 4 days late for her period with another BFN wondering if it was a chemical pregnancy.

Could the first test have just been a false positive?