Is is right using expressions like "before her coming here" in place of "before she came here"

I often use expression like these

• I came to this place before him getting here (rather than using before he got here).
• We were having a lot of fun before before her getting here (instead of before she got here).

I did not see a lot of results on the web for expressions like these, so I am wondering whether it is right or not?

As @StoneyB says, both forms are "valid". But although I don't like admitting to being "old-fashioned", I would much prefer possessive his before the gerund. Not that it matters much, because like almost all native speakers, I would always use OP's second alternatives.

Since the same construction arises with many verbs, consider these Google Books results...

before he saw it 339,000 hits

before him seeing it 421 hits

before his seeing it 5 hits

So it's understandable OP doesn't see a lot of results on the web for expressions like these. They might be "technically valid", but that means nothing if people hardly ever use them.