Pic 4 does look like a penis, but there's always a chance it could be the cord. How did she first decide it was a girl? When I had a gender scan with DD1, the sonographer explained to me that they would never say it was a girl simply because they couldn't see a penis, they had to be able to see the 3 lines that would indicate the labia. Nothing being there could just be that the angle isn't right and the boy bits are hiding! Did she point out 3 lines at all (I can't really tell on the scan pic)?
I'd definitely not trust their decision though and would be expecting a rescan to clarify things. If they won't, then wait until your 20 week scan to buy anything and hopefully they'll be able to give you a straight answer there.
It can't have been a nice experience being told you were getting a girl after 3 boys, to then be told oh no you're not. They should always make sure they're certain before they say anything x